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STAR-LAND 



BEING TALKS WITH YOUNG PEOPLE ABOUT THE 
WONDERS OF THE HEAVENS 



BY 



SIR ROBERT STAWELL BALL, F.R.S. 

LOWNl>KA\ PROFESSOR OF ASTRONOMY IN 

THE UNIVERSITY OF CAMBRIDGE 

AUTHOR OF " I'HE STORY OF THE HEAVENS." ETC. 



Illustrates 



NEW AND REVISED EDITION 



Boston, U.S.A., and London 

GIXX & COMPANY, PUBLISHERS 

iftfjc Stbrnarttm JJrcas 

1899 



■21 IBM 



46585 



Entered at Stationers' Hall 



Copyright, 1899, by 
CASSELL & COMPANY, LIMITED 



ALL RIGHTS RESERVED 



TWO COPIES RLCE1VED, 



V\<\ 



8EC0N0 COPY, 




<3 ^AA- 1 .^ 



(Co 
THOSE YOUNG FRIENDS 

WHO HAVE ATTENDED MY CHRISTMAS LECTURES 

THIS LITTLE BOOK 

IS DEDICATED 



PREFACE TO FIRST EDITION. 

It has long been the custom at the Royal Institu- 
tion of Great Britain to provide each Christmastide 
a course of Lectures specially addressed to a juvenile 
audience. 

On two occasions, namely, in 1881 and in 1887, 
the Managers entrusted this honorable duty to me. 
The second course was in the main a repetition of 
the first ; and on my notes and recollections of both 
the present little volume has been founded. 

I am indebted to my friends Rev. Maxwell Close, 
Mr. Arthur Rambaut, and Dr. John Todhunter 
for their kindness in reading the proofs. 

ROBERT S. BALL. 

Observatory, 
Co. Dublin, 

Oct. 22, 1889. 



CONTENTS. 

LECTURE I. 
THE SUN. 

PAGE 

The Heat and Brightness of the Sun — Further Benefits that we 
receive from the Sun — The Distance of the Sun — How As- 
tronomers measure the Distances of the Heavenly Bodies — 
The Apparent Smallness of Distant Objects — The Shape and 
Size of the Sun — The Spots on the Sun — Appearances seen 
during a Total Eclipse of the Sun — Night and Day — The 
Daily Rotation of the Earth — The Annual Motion of the 
Earth round the Sun — The Changes of the Seasons — Sun- 
shine at the North Pole 1 

LECTURE II. 

THE MOON. 

The Phases of our Attendant the Moon — The Size of the 
Moon — How Eclipses are produced — Effect of the Moon's 
Distance on its Appearance — A Talk about Telescopes — 
How the Telescope aids us in Viewing the Moon — Tele- 
scopic Views of the Lunar Scenery — On the Origin of the 
Lunar Craters — The Movements of the Moon — On the Pos- 
sibility of Life in the Moon . 74 

LECTURE III. 
THE INNER PLANETS. 

Mercury, Venus, and Mars — How to make a Drawing of our 
System — The Planet Mercury — The Planet Venus — The 
Transit of Venus — Venus as a World — The Planet Mars 
vii 



Vlll CONTENTS. 

PAGE 

and his Movements — The Ellipse — The Discoveries made 
by Tycho and Kepler — The Discoveries made by Newton — 
The Geography of Mars — The Satellites of Mars — How the 
Telescope aids in Viewing Faint Objects — The Asteroids, 
or Small Planets 134 



LECTURE IV. 

THE GIANT PLANETS. 

Jupiter, Saturn, Uranus, Neptune — Jupiter — The Satellites of 
Jupiter — Saturn — The Nature of the Rings — William Her- 
schel — The Discovery of Uranus — The Satellites of Uranus 
— The Discovery of Neptune . . . . . . 212 

LECTURE Y. 

COMETS AND SHOOTING STARS. 

The Movements of a Comet — Encke's Comet — The Great Comet 
of Halley — How the Telegraph is used for Comets — The 
Parabola — The Materials of a Comet — Meteors — What be- 
comes of the Shooting Stars — Grand Meteors — The Great 
November Showers — Other Great Showers — Meteorites . 255 

LECTURE VI. 

STARS. 

We try to make a Map — The Stars are Suns — The Numbers of 
the Stars — The Clusters of Stars — The Rank of the Earth 
as a Globe in Space — The Distances of the Stars — The 
Brightness and Color of Stars — Double Stars — How we find 
what the Stars are made of — The Nebulae — What the Neb- 
ulae are made of — Photographing the Nebulae — Conclusion 318 

CONCLUDING CHAPTER. 
HOW TO NAME THE STARS. 381 



STAR-LAND. 

LECTURE I. 

THE SUN. 

The Heat and Brightness of the Sun — Further Benefits that we receive 
from the Sun — The Distance of the Sun — How Astronomers measure 
the Distances of the Heavenly Bodies — The Apparent Smallness of 
Distant Objects — The Shape and Size of the Sun — The Spots on the 
Sun — Appearances seen during a Total Eclipse of the Sun — Night 
and Day — The Daily Rotation of the Earth — The Annual Motion of 
the Earth round the Sun — The Changes of the Seasons — Sunshine at 
the North Pole. 

THE HEAT AND BRIGHTNESS OF THE SUN. 

We can all feel that the sun is very hot, and we 
know that it is very big and a long way off. Let us 
first talk about the heat from the sun. On a cold day 
it is pleasant to go into a room with a good fire, and 
everybody knows that the nearer we go to the fire, the 
more strongly we feel the heat. The boy who is at 
the far end of the room may be shivering with cold, 
while those close to the fire are as hot as they find to 
be pleasant. If we could draw much nearer to the sun 
than we actually are, we should find the heat greatly 
increased. Indeed, if we went close enough, the tem- 
perature would rise so much that we could not endure 
it; we should be roasted. On the other hand, we 

l 



Z STAR-LAND. 

should certainly be frozen to death if we were trans- 
ported much further away from the sun than we are 
now. We are able to live comfortably, because our 
bodies are just arranged to suit the warmth which the 
sun sends to that distance from it at which the earth 
is actually placed. 

Suppose you were able to endure any degree of heat, 
and that you had some way of setting out on a voyage 
to the sun. Take with you a wax candle, a leaden 
bullet, a penny, a poker, and a flint. Soon after you 
have started you find the warmth from the sun increas- 
ing, and the candle begins to get soft and melt away. 
Still, on you go, and you notice that the leaden bullet 
gets hotter and hotter, until it becomes too hot to 
touch, until at last the lead has melted, as the wax 
had previously done. However, you are still a very 
long way from the sun, and you have the penny, the 
poker, and the flint remaining. As you approach closer 
to the luminary the heat is ever increasing, and at last 
you notice that the penny is beginning to get red-hot ; 
go still nearer, and it melts away, and follows the 
example of the bullet and the candle. If you still 
press onwards, you find that the iron poker, which was 
red-hot when the penny melted, begins to get brighter 
and brighter, till at last it is brilliantly white, and 
becomes so dazzling that you can hardly bear to look 
at it; then melting commences, and the poker is 
changed into liquid like the penny, the lead, and the 
wax. Yet a little nearer you may carry the flint, 
which is now glowing with the same fervor which 
fused the poker, but even the flint itself will have 



THE BURNING-GLASS. 6 

to yield at last and become, not merely a liquid like 
water, but a vapor like steam. 

You will ask, how do we learn all this ? As nobody 
could ever make such a journey, how can we feel certain 
that the sun is so excessively hot ? I know that what 




Fig. 1. — How to use the Burning-glass. 

I say is true for various reasons, but I will only mention 
one, which is derived from an experiment with the 
burning-glass, that most boys have often tried. 

We may use one of those large lenses that are 
intended for magnifying photographs. But almost any 
kind of lens will do, except it be too flat, as those in 
spectacles generally are. On a fine sunny day in sum- 
mer, you turn the burning-glass to the sun, and by 



STAB-LAND. 



holding a piece of paper at the proper distance a bright 
spot will be obtained (Fig. 1). At that spot there is 
intense heat, by which a match can be lighted, gun- 






Fig. 2. — The Noonday Gun. 

powder exploded, or the paper itself kindled. The 
broad lens collects together the rays from the sun that 
fall upon it, and concentrates them in one spot, which 
consequently becomes hot and bright. If we merely 
used a flat piece of glass the sunbeams would go 



THE KGONDAY GUN. 5 

straight through ; they would not be gathered together, 
and they would not be strong enough to burn the paper. 
The lens, you see, is not flat ; its faces are curved, and 
they thus acquire the power of bending in rays of light 
or heat, so as to unite their effect on that one point 
which we call the focus. When a great number of rays 




Fig. 3. — A Tell-tale for the Sun. 

are thus collected on the same spot, erich of them con- 
tributes a little warmth. 

Some ingenious person has turned this principle to 
an odd use, by arranging a burning-glass over a cannon 
in such a way that just when noon arrived the spot of 
light should reach the touch-hole of the cannon and fire 
it off. Thus the sun itself is made to announce the 
middle of the day (Fig. 2). 

Another application of the burning-glass is to obtain 
a record of the number of hours of sunshine in each 



6 STAR-LAND. 

day. You will understand the apparatus from Fig. 3 ; 
the lens is here replaced by a glass globe, which acts 
as a burning-glass. As the sun moves over the sky 
the bright spot of light also moves, and therefore 
burns its track on a sheet of paper marked with lines 
corresponding to the hours. When the sun is hidden 
by clouds the burning ceases, so by preserving each 
day the piece of paper, we have an unerring tell-tale, 
which shows us during what hours the sun was shining 
brightly, and the hours during which he was hidden. 
You see, the burning-glass is not merely a toy, it 
can be made useful in helping us to learn something 
about the weather. 

Another experiment with the burning-glass will also 
teach us something. Take a candle, and from its flame 
you can get a bright point at the focus. It may fall 
upon your hand, but you can hardly feel it, and you will 
readily believe that the focus is not nearly so hot as the 
candle. Even when a burning-glass is held in front of 
a bright fire there is comparatively little heat in the 
focus. By using a lens to condense the beams from an 
electric lamp, Professor Tyndall has shown how to light a 
piece of paper, and to produce many other effects. But, 
nevertheless, the focus is not nearly so hot as the arc 
between the two glowing carbons. You might move 
your finger through the focus without much incon- 
venience, but I would not recommend you to trust your 
finger between the poles of the electric light itself. The 
temperature obtained at the focus of a burning-glass 
seems thus to be always less than that prevailing at the 
source of heat itself. This principle will be equally true 



AIR BLANKETS. 7 

when we turn a burning-glass to the sun, and hence we 
know that the sun must be hotter than an^ heat which 
can be obtained by the biggest burning-glass on the 
brightest of summer days. But burning-glasses a yard 
wide have been made, and astonishing heat effects have 
been produced. Steel has thus been melted by the sun- 
beams, and so have other substances which even our 
greatest furnaces cannot fuse. Therefore the sun must 
have a higher temperature than that of molten steel; 
higher, indeed, than any temperature we can produce 
on the earth. 

I have tried to prove to you that the sun is very 
hot ; but it would be well to see what arguments might 
be used on the other side. Indeed, it is by considering 
objections that we often learn. So I shall tell you of a 
difficulty that was once raised when I was endeavoring 
to explain the heat of the sun to an intelligent man. 
"I am sure," said my friend, "that you must be quite 
wrong. You said that the nearer you got to the sun 
the hotter it would be ; but I know this to be a mistake. 
When tourists go to Switzerland, they sometimes climb 
very high mountains. But the top of a mountain, of 
course, is nearer the sun than below ; and so, if the sun 
were really hot, the climber should have found it much 
warmer on the top of the mountain than at its base. 
But every one knows that there is abundant ice and 
snow on lofty Alpine summits, while down below in the 
valleys there may be at the same time excessively warm 
weather. Does it not therefore seem that the nearer we 
go to the sun the colder it is, and the further we are 
from the sun the warmer it is ? " 



8 STAR-LAND. 

But my friend was quite wrong in his argument. 
The coldness of the mountain tops depends upon some- 
thing which he had not taken into account. There 
is something else besides the sun which helps to 
make us so warm and comfortable. This other essen- 
tial thing is more or less deficient at great heights. 
You know that we live by breathing air, and we find 
air wherever we go, over land and sea, all round the 
earth. Those who ascend in balloons are borne upwards 
by the air, and thus we can show that air extends for 
miles and miles over our heads, though it becomes 
lighter and thinner the loftier the elevation. 

We not only utilize the air for breathing, but it is 
also of indispensable service to us in another way. It 
acts as a blanket to keep the earth warm ; indeed, we 
ought rather to describe the air as a pile of blankets one 
over the other. These air blankets ^enable the earth 
to preserve the heat received from the sunbeams by 
preventing it from escaping back again into space. 
Thus warmth is maintained, and our globe is ren- 
dered habitable. You see then, that for our comfort 
we require not only the sun to give us the heat, but 
also the set of blankets to keep it when we have got 
it. If we threw off the blankets we should be uncom- 
fortable, though the sun were as bright as before. A 
man who goes to the top of a mountain at mid-day does 
approach the sun to some extent, and, so far as this 
goes, he ought no doubt to feel warmer, but the gain 
is far too small to be thought of. Even at the top of 
Mont Blanc the increase in heat due to the approach 
to the sun would be only one ten-millionth part of the 



WHAT THE SUN DOES FOR US. 9 

whole. This would be utterly inappreciable; even a 
thermometer would not be delicate enough to show it. 
On the other hand, by ascending to the top of the 
mountain, the climber has got above the lower regions 
of the air ; he has not, it is true, reached even halfway 
to the upper surface — that is still very far over his 
head — but the higher layers of the atmosphere are 
so very thin that they form most indifferent blankets. 
The Alpine climber on the top of the mountain has 
thus thrown off the best portion of his blankets, and 
receives a chill; while the gain of heat arising from 
his closer approach to the sun is imperceptible. Per- 
haps you will now be able to understand why eternal 
snow rests on the summits of the great mountains. 
They are chilled because they have not so many air 
blankets as the snug valleys beneath. 

The brightness of the sun is among the most wonder- 
ful things in nature, and there are three points that I 
ask you to remember, and then indeed you will agree 
with Milton, that the sun is " with surpassing glory 
crowned." First think of the beauty and brilliancy of 
a lovely day in June. Then remember that all this 
flood of light comes from a single lamp at a most 
tremendous distance ; and thirdly, recollect that the 
sun is not like a bull's-eye lantern, concentrating all 
his light specially for our benefit, but that he diffuses 
it equally around, and that we do not get on this earth 
the two-thousand-millionth part of what he gives out 
so plenteously ! When we think of the brightness of 
day, of the distance from which the light has come, 
though Nature has not adjusted any vast lenses to direct 



10 STAR-LAND. 

the light specially in our direction, we begin to com- 
prehend the sun's true magnificence. 

FURTHER BENEFITS THAT WE RECEIVE FROM 

THE SUN. 

I want to show you how great should be the extent 
of our gratitude to the sun. Of course, on a bright 
summer's day, when we are revelling in the genial 
warmth and enjoying the gladness of sunshine, it needs 
no words to convince us of the utility and of the benefi- 
cence of sunbeams. So we will not take midsummer. 
Let us take midwinter. Take this very Christmas sea- 
son when the days are short and cheerless, the nights 
are long and dark and cold. We might be tempted to 
think that the sun had well-nigh forgotten us. It is 
true he only seems to pay us very occasional visits, and 
between fogs and clouds we in England see but little 
of him; but, visible or invisible, the sun incessantly 
tends us, and provides for our welfare in ways that 
perhaps we do not always remember. 

Let me give an illustration of what I mean. You 
will go back this dull and cold afternoon to the happy 
home where your Christmas holidays are being enjoyed. 
It will be quite dark ere you get there, for the sun in 
these wintry days sets so very early. You will gather 
around a cheerful fire. The curtains will be drawn, the 
lamps will be lighted, and the disagreeable weather out- 
side will be forgotten in the pleasant warmth and light 
within. Five o'clock has arrived, the pretty wicker table 
has been placed near mamma's chair ; on it are the cups 
and saucers and the fancy teapot. Under the table is 



HOW COAL IS PRODUCED. 11 

a little shelf, with some tempting cakes and a tender 
muffin. Two or three welcome friends have joined the 
little group, and a delightful half-hour is sure to follow. 

But you may say, " What have tea and muffins, 
lamps and fireplaces to do with the sun? Are they 
not all mere artificial devices, as far removed as pos- 
sible from the sunbeams or the natural beauties which 
sunbeams create ? " Well, not so far, perhaps, as you 
may think. Let us see. 

Poke up the fire, and while it is throwing forth that 
delicious warmth, and charming but flickering light, 
we will try to discover where that light and heat have 
come from. No doubt they have come from the coal, 
but then, whence came the coal? It came from the 
mine, where brave colliers hewed it out deep under the 
ground, and then it was hoisted to the surface by steam 
engines. Our inquiry must not stop here, for another 
question immediately arises, as to how this wonderful 
fuel came into the earth ? When we examine coal care- 
fully, by using the microscope to see its structure, we 
find that it is not like a stone ; it is composed of trees 
and other plants, the leaves and stems of which can be 
sometimes recognized. Indeed, the fossil trunks and 
roots of the great trees are occasionally conspicuous 
in the coal-pit. It is quite plain that these are only 
the remains of a vegetation which was formerly grow- 
ing and flourishing, and on further inquiry we learn 
that coal must have been produced in the following 
manner : — 

Once upon a time a great forest flourished. The 
sun shone down on this forest, and it was watered 



12 STAR-LAND. 

by genial showers, while insects and other creatures 
sported in its shades. It is true that the trees and 
plants were not like those we now see about us. They 
were more like ferns and mare's-tails and gigantic club- 
mosses. In the fulness of time they died, and fell, and 
decayed, and others sprang up to meet the like end. 
Thus it happened that, in course of ages, the remains 
of leaves, and fruits, and trunks accumulated over the 
soil. The forest was situated near the seashore, and 
then a remarkable change took place — the land began 
slowly to sink. You need not think that this is im- 
possible. Land has often been known to change its 
level gradually. In fact, a sinking process is slowly 
going on now in many places on the earth, while the 
land is rising in other localities. As the forest gradually 
sank lower and lower, the sea- water began to inundate 
it, and all the trees perished until, at last, deep water 
submerged the surface which had once been covered 
by a fine forest. At the bottom of this sea lay the 
decaying vegetation. 

That which was the destruction of the growing 
forest, proved to be the means of preserving its 
remains, for, then as now, the rivers flowed into the 
sea, and the waters of the rivers, especially in times 
of flood, carried down with them clay or mud, held in 
suspension. Upon the floor of the ocean this material 
was slowly deposited ; and thus a coating of mud over- 
lay the remains of the forest. In the course of ages, 
these layers grew thick and heavy, and hardened into a 
great flat rock, while the trunks and leaves underneath 
were squeezed together by the weight, and packed into 



HOW COAL IS PRODUCED. 13 

a solid mass which became black, and in the course of 
time was transformed into coal. 

After ages and ages had passed by, the bed of the 
sea ceased to sink, and began slowly to rise. The water 
over the newly made layers of stone became shallower, 
and at last the floor was raised until it emerged from 
the sea. But, of course, it would not be the original 
ground which formed the surface of the newly uncov- 
ered land. The sheets of consolidated clay lay on the 
top ; over the fresh surface life gradually spread, until 
man himself came to dwell there, while far beneath his 
feet the remains of the ancient vegetation were buried. 

When we now dig down through the rocks we come 
upon the portions of trees and other plants which the 
lapse of time, and the influence of pressure, have turned 
from leaves and wood into our familiar coal. 

That ancient forest grew because sunbeams abounded 
in those early times, and nourished a luxuriant vegeta- 
tion. The heat and the light then expended so liberally 
by the sun were seized by the leaves of flourishing 
plants, and were stored away in their stems and foliage. 
Thus it is that the ancient sunbeams have been pre- 
served in our coal-beds for uncounted thousands of 
years. When we put a lump of coal on our fire this 
evening, and when it sends forth a grateful warmth 
and cheerful light, it but reproduces for our benefit 
some of that store of preserved sunbeams of which our 
earth holds so large a treasure. Thus, the sun has 
contributed very materially to our comfort, for it has 
provided the fire to keep us warm. 

The orb of day has, however, ministered further to 



14 STAR-LAND. 

our tea party, for has it not produced the tea itself? 
The tea grew a long way off, most likely in China, where 
the plant was matured by the warmth of the sunbeams. 
From China the tea-chests were brought by a sailing 
vessel to London ; the ship performed this long voyage 
by the use of sails, blown by what we call wind, which 
is merely the passage of great volumes of air as they 
hurry from one part of the earth to another. 

We may ask what makes the air move, for it will 
not rush about in this way unless there be considerable 
force to drive it. Here again we perceive the influence 
of the sun. Tracts of land are warmed by the genial 
sunbeams. The air receives the heat from the land, 
and the warm air is buoyant and ascends, while cooler 
air continually flows in to supply its place. To do this 
it has, of course, to rush across the country, and thus 
wind is caused. All the air currents on our earth are 
consequently due to the sun. You see, therefore, how 
greatly we are indebted to our brilliant luminary for the 
enjoyment of our tea-table. Not only has the sun given 
us the coal and the tea, but it has actually provided the 
means by which the tea was carried all the way from 
China to our own shores. 

We can also trace the connection between the hot 
water and the sun. Of course, the water has come 
immediately from the kettle, and that has been taken 
from the fire, and the fire was produced by sunbeams. 
Thus we learn that it is the warmth of the .sun that has 
made the water boil. If you visit the water-works you 
will see great reservoirs. In some cases they have been 
filled by a river, sometimes the water is pumped from a 



HOW THE SUN PROVIDES OUR TEA. 15 

deep well in the ground, sometimes it is the surface- 
water caught on a mountain side. Whatever be the 
immediate source of our water supply, the real origin is 
to be sought, not in the earth beneath, but in the 
heavens above. All the water we use day by day has 
come from the clouds. It is the clouds which sent 
down the rain, or sometimes the snow, or the hail, and 
it is this water from the clouds which fills our rivers. 
It is this water also which sinks deep into the earth and 
supplies our wells, so that from whatever apparent 
source the water seems to have come, it is indeed the 
clouds which have been the real benefactors. The water 
in your teacup to-night was, a little while ago, in a cloud, 
floating far overhead in the sky. 

We may look a little further and find whence the 
clouds have come. It is certain that clouds are merely 
a form of steam or vapor of water, and as they are so 
continually sending down rain on the earth, there must 
be some means by which their supply will be replen- 
ished. Here again our excellent friend the sun is to be 
found ever helping us secretly, if not helping us openly. 
He pours down his rich and warm beams on the great 
oceans, and the heat turns some of the water into vapor, 
which, being lighter than the air, ascends upwards for 
miles. There the vapor often passes into the form of 
clouds, and the winds waft these clouds to refresh the 
thirsty lands of the earth. Thus, you see, it is the sun 
which procures for us water from the great oceans which 
cover so much of our globe, and sends it on by the 
winds to supply our water-works, and fill our teapots. 
Notice another little kindliness of our great benefactor. 



16 STAR-LAND. 

The water of the oceans is quite salt. But we could 
not make tea with salt water, so the sun, when lifting 
the vapor from the sea, most thoughtfully leaves all the 
salt behind, and thus provides us with the purest of 
sweet water. 

That nice muffin was baked by the sun, toasted by 
the sun, and made from wheat grown by the sun. If 
the wheat was ground in a wind-mill, then the sun 
raised the wind which turned the mill. Perhaps the 
flour-mill was driven by steam, in which case the sun, 
long ago, provided the coal for the boiler. The miller 
might have lived on a river and used a water-mill, but 
if he did, then here again the sun actually did the work. 
The sun raised the water to the clouds, and after it had 
fallen in rain, and was on its way back to the sea, its 
descent was utilized to turn the water-wheel. The water 
derives its power to turn the mill from the fact that it 
is running downhill, but it could not run down unless 
it had first been raised up ; and thus it is indeed the sun 
which drives the water-wheel. Nor can the baker dis- 
pense with the sun's aid even if he rejected wind-mills, or 
steam-mills, or water-mills, and determined to grind the 
corn himself with a pestle and mortar. Here, at least, 
it might be thought that it is a man's sinews and muscles 
that are doing the work, and so no doubt they are. But 
you are mistaken if you think the sun has not rendered 
indispensable aid. The sun has just as surely provided 
the power which moves the baker's arms as it has raised 
the wind which turned the wind-mill. The force exerted 
in grinding with the pestle has been derived from the 
food that the man has eaten ; that food was grown by 



THE DISTANCE OE THE SUN FROM US. 17 

the sun, and the man received from the food the energy- 
it had derived from the sun's heat. So that, look at it 
any way you please, even for the grinding of the wheat 
to make the muffin for your tea party, you are wholly 
indebted to the sun. 

It is the sun which has bleached the tablecloth to 
that snowy whiteness. The sun has given those bright 
colors which look so pretty in the girls' dresses. With 
how much significance can we say and feel that light is 
pleasant to the eye, and what prettier name than Little 
Sunbeam can we have for the darling child who makes 
our home so bright ? 

THE DISTANCE OF THE SUN. 

The sun is a very long way off. It is not easy for 
you to imagine a distance so great, but if you want to 
learn astronomy you must make the attempt. This is 
the first measurement that we shall have to make on 
our way to that far-off country called Star-Land ; but 
long as we shall find it to be, we shall afterwards have 
to consider distances very much longer. When you are 
out in the street, or taking a walk in the country, you 
can see at once that this man is near, or that house is 
far, or that mountain is many miles away. This is 
because you have other objects between to help you to 
judge of the distances of these different objects. You 
will see, for example, that there are many houses or 
farmyards, and you will notice hedges dividing different 
fields between you and the mountain. You also see 
that there are woods and parks, and perhaps stretches 
of moorland extending up the slopes. You have an 



18 STAR-LAND. 

impression that the farmyards and fields are of consid- 
erable size, and that the woods or moors are wide and 
extensive ; and putting these things together, you 
realize that the mountain must be miles away. 

But when we look at the sun we have no aids con- 
veniently placed to help us in judging his distance. 
There are no intervening objects, and merely gazing 
at the sun helps us but little in obtaining any accurate 
knowledge. We must go to the astronomer and ask 
him to tell us how far he has found the sun to be, and 
then we must also beg from him some explanation of 
the method he has used in making his measurements. 

It has been found that the sun is, on the average, 
about ninety-three millions of miles from the earth ; but 
sometimes it is a little further and sometimes it is a little 
nearer. Let us first try to count 93,000,000. The easiest 
way will be to get the clock to do this for us ; and here 
is a sum that I would suggest for you to work out. 
How long will the clock have to tick before it has made 
as many ticks as there are miles between the earth and 
the sun ? Every minute the clock, of course, makes 
60 ticks, and in 24 hours the total number will reach 
86,400. By dividing this into 93,000,000 you will find 
that more than 1076 days, or nearly three years, will 
be required for the clock to perform the task. 

We may consider the subject in another way, and 
find how long an express train would take to go all the 
way from the earth to the sun. We shall suppose the 
speed of the train to be 40 miles an hour ; and if 
the train ran for a whole day and a Avhole night with- 
out stopping, it would then accomplish 960 miles. In 



THE ADVANTAGES OF TWO EYES. 19 

a year the distance travelled would reach 350,400 miles, 
and by dividing this into 93,000,000 we arrive at the 
conclusion that a train would have to travel at a pace 
of 40 miles an hour, not alone for days and for weeks 
and for years, but even for centuries. Indeed, not until 
265 years had elapsed would the mighty journey have 
been ended. Even though King Charles I. had been 
present when the train began to move, the destination 
would not yet have been reached. No one who started 
in the train could expect to reach the end of the trip. 
That would not occur till the time of his great-great- 
grandchildren. 

HOW ASTRONOMERS MEASURE THE DISTANCES OF THE 
HEAVENLY BODIES. 

I shall so often have to speak of the distances of the 
celestial bodies that I may once for all explain how it is 
that we have been able to discover what these distances 
are. This would be a very puzzling matter if we were 
to try and describe it fully, but the principle of the 
method is not at all difficult. Do you know why you 
have been provided with two eyes ? It is undoubted 
that one of the reasons is to aid you in estimating dis- 
tances. You see this boy (Fig. 4) judges of the distance 
of his finger by the inclination of his two eyes when 
directed at it. In a similar way we judge of the dis- 
tance of a heavenly body by making observations on it 
from two different stations. 

I shall illustrate our method of measuring the actual 
distance of a body in the heavens by showing you how 
we can find the height of that large india-rubber ball 



20 STAR-LAND. 

which is hanging from the ceiling. Of course, I do not 
intend to have a measuring tape from the ball itself, 
because I want to solve the problem on the same princi- 




Fig. 4. — Two Eyes are better than One. 

pie as that by which we measure the distance of the sun 
or of any other celestial body which we cannot reach. 
I will ask the aid of a boy and a girl, who will please 
stand one at each end of the lecture table. The appa- 
ratus we shall want is very simple ; it consists of two 
cards and a pair of scissors. The boy will kindly shape 
his card to such an angle that when he holds it to his 
eye one side of the angle shall point straight at the 
little girl, and the other side shall point straight at the 
ball, just as you see in the picture (Fig. 5). The girl 
will also please do the same with her card, so that along 
one side she just sees the little boy's face, while the other 



MEASUKING DISTANCE. 



21 



side points up to the ball. It will be necessary to cut 
these angles properly. If the angle be too big, then 
when one side points to the boy's face, the other will be 



i 



''lfli||^ : ' : ' :r: 




Fig. 5. — How we measured the Height of the Ball. 

directed above the ball. If the angle on the card be 
too small, then one side will be directed below the ball, 
while the other is pointed to the boy. The whole 
accuracy of our little observations depends upon cutting 




2% STAR-LAND. 

the card angles properly. When they have been truly 
shaped it will be easy to find the distance of the ball. 
We first take a foot rule and measure the length of our 
table from one of our young friends to the other. That 
length is twelve feet, and to discover 
the distance of the ball we must make 
a drawing. We get a sheet of paper, 
and first rule a line twelve inches 
long. That will represent the length 
of the table, it being understood that 
each inch of the drawing is to corre- 
spond to a foot of the actual table. 
Let the end where the girl stood 

A 12 inches •» & 

Fig. 6. — This is what be marked B, and that of the boy, A, 
we wanted the Cards ail( j now bring the cards and place 
them on the line just as shown in the 
figure. The card the girl has shaped is to be put so 
that the corner of it lies at b, and one edge along B A. 
Then the boy's card is to be so put that its corner is 
at A and one edge along A b. Next with a pencil we 
rule lines on the other edges of the cards, taking care 
that they are kept all the time in their proper positions. 
These two lines carried on will meet at c ; and this 
must be the position of the ball on the scale of our little 
sketch. It only now remains to take the foot rule and 
measure on the drawing the length from A to C. I 
find it to be twenty inches, and I have so arranged it 
that the distance from b to c is the same. 

I do not intend to trouble you much with Euclid in 
these lectures, but as many of my young friends have 
learned the sixth book, I will just refer to the well- 



A TASK FOR ASTRONOMERS. 23 

known proposition, which tells us that the lengths of 
the corresponding sides of two similar triangles are pro- 
portional. We have here two similar triangles. There 
is the big one with the boy at one corner, the girl at 
the other, and the ball overhead. Here is the small 
triangle which we have just drawn. These triangles 
are similar because they have got the same angles, and 
it was to insure that they should have the same angles 
that we were so careful in shaping the cards. As these 
two triangles are similar, their sides must be propor- 
tional. We have agreed that the line A B, which is 
twelve inches long, is to represent the length of the 
table between the little boy and girl. Hence the dis- 
tance, A c, must, on the same scale, be the interval 
between the ball and the boy at the end. This is 
twenty inches on the drawing, and therefore the actual 
distance from the end of the table to the ball is twenty 
feet. 

Hence you see that without going up to the ball or 
having a string from it, or in any other way making 
direct communication with it, we have been able to 
ascertain how far up in the air the ball is actually hung. 
This simple illustration explains the principle of the 
method by which astronomers are able to learn the dis- 
tances of the different celestial bodies from the earth. 
You must think of the sun, the moon, and the stars as 
globes supported in some manner over our heads, and 
we seek to discover their distances from measurements 
of angles made at the ends of a base-line. 

Of course, astronomers must choose two stations 
which are far more widely separated than are those in 



24 



STAR-LAXD. 



Sun 



our little experiment. In fact, the greater the interval 
between the two stations, the better. Astronomers 
require a much longer distance than from one side of 
this room to the other, or from one side of London to 
the other side. If it were merely a balloon at which 
we were looking, then, when one observer at one side 
of London and another at the opposite side shaped their 
cards carefully, we should be able to tell the height 
of the balloon very easily. But as 
the sun is so much further off than 
any balloon could ever be, we must 
separate the observers much more 
widely. Even the breadth of Eng- 
land would not be enough, so w r e 
have to make them separate more and 
more until they are as widely divided 
as it is possible for anj^ two people on 
this earth to be. One astronomer 
takes up his position at A (Fig. 7), 
and the other at the opposite side at 
B, so that they can both see the sun. 
They are obliged to use a much 
more accurate w r ay of measuring the 

I. — mis would be i ±.1 i ij_- i *xi 

■ Base-line when aR gl es than by cutting out cards with 

pairs of scissors ; and as the astrono- 
mer at A is not able to see his friend 
at B, it becomes no easy matter to measure the angles 
accurately. However, we shall not now^ trouble our- 
selves about such difficulties. It may suffice for the 
present to know that the angles are measured by deli- 
cate and very accurate instruments used by astronomers. 




Fig. 7. — This would be 
our 

finding the Sun's 
Distance. 



WHY DISTANT THINGS LOOK SMALL. 25 

They will not, indeed, make a little sketch such as 
sufficed for our purpose. They make a calculation 
which is a much more accurate way of effecting true 
measurement. The astronomers know the size of the 
earth, and thus they know how many thousands of 
miles lie between the two stations where the observa- 
tions are made. This distance means in their calcula- 





Fig. 8. — The nearer you are, the bigger the Globe looks. 

tion just what the length of the table did in our sketch. 
From each end of the line they set off an angle just as 
we did, and the astronomer must use the principle of 
similar triangles which he finds in Euclid, just §s we had 
to do. At last, when they have calculated the sides of 
their triangle, they obtain the distance of the sun. 

THE APPARENT SMALLNESS OF DISTANT OBJECTS. 

I ought here to explain a principle which those who 
are learning about the stars must always bear in mind. 
The principle asserts that the further a body is, the 
smaller it looks. Perhaps this will be understood from 
the adjoining little sketch (Fig. 8). It represents a 
great globe, on which oceans and continents are shown, 



26 STAB-LAND. 

and you see a little boy and a little girl are looking at 
the globe. The girl stands quite close to it, and I have 
drawn two dotted lines from her eye, one to the top of 
the globe, and the other to the under surface. If she 
wants to examine the entire side of the globe which is 
visible to her, she must first look along the upper dotted 
line, and then she must turn her glance downwards 
until she comes to the lower line, and having to turn 
her eyes thus up and down she will think the globe is 
very big, and she will be quite right. The boy is, as 
you see, on the other side of the globe, but I have put 
him much further off than the girl. I have also drawn 
two dotted lines from his eye to the globe, and it is 
plain that he will not have to turn his head much up 







Fig. 9. — The Globe is so far off that it lies beyond the Picture. 
The dotted lines show how small it seems. 



and down to see the whole globe. He can take it all 
in at a glance, and to him, therefore, the globe will 
appear to be comparatively small, because he is suffi- 
ciently far from it. The more distant he is, the smaller 
it will appear. You can easily imagine that, if the 
globe were far enough, the two lines that would include 
the whole would be like those shown (Fig. 9), in which 
the globe is so distant that it cannot be seen in the 
picture. The apparent size of the globe, which is 
really measured by the angle between these two lines, 



WHY DISTANT THINGS LOOK SMALL. 27 

would always be smaller and smaller according as the 
distance was greater. Now you can understand why 
an object seems smaller the further away it is ; indeed, 
when sufficiently far, the object ceases to be visible 
at all. 

I could give many illustrations of the diminution of 
size by distance, and so, doubtless, could you. Every 
boy knows that his kite looks smaller and smaller the 
greater the length of string that he lets out. I have 
seen in the West of Ireland a bird that seemed like a 
little speck high up near the clouds, but from its flight 
and other circumstances I knew that the speck was not 
a little bird. It was, indeed, a great eagle, which was 
dwarfed by the elevation to which it had soared. 

It is in astronomy that we have the best illustrations 
of this principle. Enormous objects seem to be small 
because they are so very far off. You must therefore 
always remember that although an object may appear 
to be small, this appearance may be only a delusion. 
It may be that the object is very big, but very distant. 
In astronomy, this is almost always the case, there is so 
much room above us, around us, on all sides in space. 
Look up at the ceiling. It certainly does not bound 
space, for there is another side to it ; and then there is 
the roof of the house. But the roof is not a boundary, 
for, of course, there is the air above it, and then, higher 
up still, there are the clouds, and so we can carry our 
imagination on and on through and beyond the air up 
to where the stars are, and still on and on. And as 
there is unlimited room, the celestial bodies take advan- 
tage of it, and are, generally speaking, at distances so 



28 ' STAR-LAND. 

gigantic that, no matter how small they may appear, 
their smallness is merely deceptive. 

Let us try to illustrate in another way the exceeding 
remoteness of the sun. So please imagine that you 
were on the sun, and that you took a view of our earth 
from that distance. To find out what we must expect 
to see, let us think of a balloon voyage. If you were 
to go up in a balloon, you would at first see only the 
houses, or objects immediately about you, but as you 
rose the view would become wider and wider. You 
would see that London was surrounded by the country, 
and then, as you still soared up and up, the sea would 
become visible, and you would be able to trace out the 
coasts, east and west and south. If, in some way, you 
could soar higher than any balloon could carry you, the 
whole of the British Islands would presently lie spread 
like a map beneath. Still on and on, and then the 
continent of Europe would be gradually opened out, 
until the great oceans, and even other continents, would 
at last be caught sight of, and then you would perceive 
that our whole earth was indeed a globe. The higher 
you went, the less distinctly would you be able to see 
the details on the surface. At last the outlines of the 
continents and oceans would facie, and you would begin 
to lose any perception of the shape of the earth itself. 
Long ere you had reached the distance of the sun, the 
earth would look merely as the planet Venus now does 
to us. It is instructive to consider how small our earth 
would seem if it were possible to view it from the sun. 
Think of that very familiar little globe, a lawn-tennis 
ball, which is two and three-quarter inches in diameter. 



SHAPE AND SIZE OF THE SUN. 29 

But suppose a tennis ball were at the opposite side of 
the street, or still further away ; suppose, for example, 
that it were half a mile away, what could you expect 
to see of it? And yet the earth, as seen from the sun, 
would appear to be no larger than a tennis ball would 
look when viewed from a distance of half a mile. 

THE SHAPE AND SIZE OE THE SUN. 

We have spoken of the heat of the sun, how hot he 
is; of the distance of the sun, how far he is; and now 
we must say a little about the size of the sun ; and also 
about his shape. It is plain that the sun is round, that 
it has the shape of a ball. We are sure of this because, 
though a plate is circular, yet, if it were placed so that 
we only saw it edgeways from a distance, it would not 
appear to be round. The sun is always rotating, and 
as it always seems to be a circle, we are therefore cer- 
tain that the true shape of the sun must be globular, 
and not merely circular like a flat plate. 

In the middle of the day, when the sun is high in the 
heavens, it is impossible for us to form a notion of the 
size of the sun. People will form very different esti- 
mates as to his apparent bigness. Some will say he 
looks as large as a dinner plate, but such statements 
are meaningless, unless we say where the plate is to be 
held. If it be near the eye, of course the plate may 
hide the sun, and, for that matter, everything else also. 
If the plate were about a hundred feet away, then it 
would often hide the sun. If the plate were more than 
a hundred feet distant, then it could not hide the sun en- 
tirely, and the further the plate, the smaller it would seem. 



30 



STAR-LAXD. 



No means of estimating the sun's size are available 
when his orb stands high in the heavens. But when 
he is rising or setting, we see that he passes behind 
trees or mountains, so that there are intervening ob- 




Fig. 10. — A Sunset viewed from Marseilles {Marcus Codde). 

jects with which we can compare him ; then we have 
actual proof that the sun must be a very large body 
indeed. 

I give here a picture, by Marcus Codde, taken from a 
French journal, VAstronomie, which gives a charming 



COMPARISONS. 31 

illustration of a sunset at Marseilles (Fig. 10). If you 
wish to see that the sun is bigger than a mountain, 
you may go to the top of Notre Dame de la Garde, 
but you must choose either the 10 th of February or the 
31st of October for your visit, because it is only on the 
evenings of those days that the sun sets in the right 
position. 

On both these evenings the sun sinks directly behind 
Mount Carigou. in the Pyrenees ; this mountain is a long 
way from Marseilles — no less, indeed, than one hundred 
and fifty-eight miles. But the mountain is so lofty, 
that when the sky is clear, the summit can be distinctly 
seen upon the sun as a background, in the way shown in 
the picture. This must be a very pretty sight, and it 
teaches us an important lesson. The sun is further 
away than the mountain, and yet you see the sun on 
both sides of the mountain, and above it. Here, then, 
we learn without any calculations, that the sun must be 
bigger than the upper part of a great mountain in the 
Pyrenees. 

When we calculate the size of the sun from the 
measurements made by astronomers, we discover that 
it is much bigger than Mount Carigou; we see that 
even the entire range of the Pyrenees, the whole of 
Europe, and even our whole globe, are insignificant by 
comparison. 

There is a football on the table, shown in Fig. 11. 
We shall suppose it to represent the sun ; we shall now 
choose something else to represent the earth. We must, 
however, exhibit the proportions accurately. A tennis 
ball will not do ; it is far too large. The fact is, the 



32 



STAR-LAND. 



width of the earth is less than the one-hundredth 
part of the width of the sun. The tennis ball is, how- 
ever, only a quarter the width of the football, so we 
must choose something a good deal smaller. I try 
with a marble, even with the smallest marble I can 
find, but when I measure it, I find that one hundred 
such marbles, placed side by side, would be far longer 
than the width of the football ; I must therefore look 
for something still smaller. A grain of small-sized shot 
will give the right size for the model of our earth. 




Fig. 11. — How we compare the Earth and the Sun. 



About one hundred of these grains placed side by side 
will extend to a length equal to the width of the 
football. Now you will be able to form some con- 
ception of how enormous the sun really is. Think of 



SUN-SPOTS. 33 

this earth, how big we find it when we begin to travel. 
What a tremendous voyage we have to take to get to 
New Zealand, and even then we have only got half- 
way round the globe. Then think that the sun is in 
the same proportion bigger than the earth as that foot- 
ball is bigger than that grain of shot. If a million of 
such grains of shot were melted and cast into one 
globe, it would not be so large as that football. If a 
million globes, as large as our earth, could be united 
together, no doubt a vast globe would be produced, but 
it would not be so large as the sun. Think of a single 
house, with three or four people living in it, and then 
think of this mighty London, with its millions of inhab- 
itants. The house will represent our earth, while great 
London represents the sun ! 

THE SPOTS ON THE SUN. 

I have shown you that the sun is intensely hot, and 
a very long way off, and enormously big. And now we 
have to describe the appearance of the surface of the sun 
when we examine it closely. 

If you get a piece of very dark glass, or if you smoke 
a piece of glass over a candle, then you can look directly 
at the sun with comfort. A nicer plan is to prick a 
pinhole in a card, through which you can look at the 
sun without any inconvenience. Generally speaking, a 
view of the sun in this way will show you only a uni- 
formly bright surface. To study the face of our great 
luminary carefully, you must use the aid which the 
telescope gives to the astronomer. A very good way of 
doing this is shown in Fig. 12. A small telescope, 



34 



STAR-LAND. 



fixed on a stand, is pointed to the sun, and, the eyepiece 
being drawn out somewhat further than when direct 
observations are being made, the sun draws its own 




Fig. 12. — Looking at the Sun. 

picture on a screen. This may be examined without 
any inconvenience, or without the necessity for any 
protection to the eye, and a number of young astron- 
omers can all view the sun at the same moment. On 
such a picture you will generally see the brilliant sur- 
face marked with dark spots, which are sometimes as 
numerous as in the case represented in Fig. 13. These 



SUN-SPOTS. 35 

spots present very different appearances according to 
circumstances. One such spot when seen with a very 
powerful telescope showed the wonderful structure 
which is represented in Fig. 14. 

The visible surface of the sun is entirely formed of 
intensely heated vapors. We might almost say that 
the spots are holes, by which we can look through the 




Fig. 13. — This is what the Sun sometimes looks like. 

brilliant surface to the interior and darker parts. Some- 
times the spots close up, and fresh ones will open else- 
where. Now and then the whole surface is mottled 
over in a remarkable way. I give here a picture which 
was taken from Mr. Nasmyth's beautiful drawing, in 
which he shows how the sun sometimes assumes the 



36 



STAR-LAND. 



appearance which has been likened to willow leaves 
(Fig. 15). This appearance was very noticeable in the 
great spot of September, 1898. 

The spots often last long enough to demonstrate a 
remarkable fact. We must remember that the sun is a 
great globe, and that it is poised freely in space. There 
is nothing to hold it up, and there is nothing to prevent 




Fig. 14. — A Sun-spot {after Janssen). 



it from turning round. That it does turn round, we 
can prove by careful observation of the spots. I can 
best illustrate what I want by Fig. 17, which shows six 
imaginary pictures. The first represents the sun on the 
1st day of the month; the next shows it five days later, 
on the 6th ; another view is five days later still, on the 
11th ; and so on until the last picture, which corresponds 
to the 26th. You see, on the first day there is a spot 



PROVING THAT THE SUN TURNS ROUND. 37 

near the left edge; by the 6th, this spot is near the 
middle ; by the 11th, it is near the right edge ; then you 







% : ^k ■'■ :>\ N - * "• ' '^ • £ ■> '■ '^ ' v -f •>; \'y t •': 






Fig. 15. — Nasmyth's Drawing of the Willow-leaved Structure of 
the Sun. 

do not see it at all on the 16th, or on the 21st; but on 
the 26th it is back in the same place from which it 



38 



STAR-LAND. 



started. We find other spots to have a similar history. 
They appear to move across the face, and then to return 
in a little less than four weeks to the same place where 
they were originally noticed. These appearances can be 




Fig. 16. — Spot nearing the Sun's Edge. 

illustrated very simply by cutting a small hole through 
the rind of an orange down to the white interior skin, 
which may be darkened with ink. Put a knitting 
needle through the axis of the orange, and then turn it 
slowly round. The spot will be found to go through 



HOW THE SPOTS HELP US. 



39 



the changes that we have seen. We start with the spot 
near the left, it moves across the face, and then passes 
to invisibility by moving behind the globe until it reap- 
pears again, after having moved round the back. As 
the same may be observed with every spot which lasts 
long enough, we learn that the changes in the places 
must be produced by the turning round of the sun. 
Here you see is the way in which an astronomical dis- 




Fig. 17. — How the Sun turns round. 

co very is made. We first observe the fact that the 
spots do always appear to move. Then we try to 
account for this, and we find a very simple explanation, 
by supposing that the whole sun, spots and all, turns 
steadily round and round. It can also be proved in a 
very conclusive manner that no other explanation is 
possible. This rotation of the sun is always going on 
uniformly, and some curious consequences follow from 
it. The view of the sun which is turned towards us 



40 STAR-LAND. 

to-day is quite different from that which was towards us 
a fortnight ago, or from that which we shall see in a 
fortnight hence. There is no actual or visible axis 
about which the sun rotates. In this the sun is like 
the earth and other celestial bodies. 

APPEARANCES SEEN DURING A TOTAL ECLIPSE 

OF THE SUN. 

For a great deal of our knowledge about the sun 
we are indebted to the moon. It will sometimes 
happen that the moon comes in between us and the 
sun, and produces an eclipse. At first you might 
think that an eclipse would only have the effect of 
preventing us from seeing anything of the sun, but it 
really reveals most beautiful and interesting objects, of 
whose existence we should otherwise be ignorant. The 
great luminary has curious appendages which are quite 
hidden under ordinary circumstances. In the full glare 
of day the dazzling splendor of the sun obliterates and 
renders invisible these appendages, which only shine with 
comparatively feeble light. It fortunately happens that 
the moon is just large enough to intercept the whole of 
the direct light from the sun, or rather, I should say, 
from the central parts of the sun. Surrounding that 
central and more familiar part from which the brilliancy 
is chiefly derived is a remarkable fringe of delicate and 
beautiful objects which are self-luminous no doubt, but 
with a light so feeble that when presented to us amid 
the full blaze of sunlight they are invisible. When, 
however, the moon so kindly stops all the stronger 
beams, then these faint objects spring into visibility, 



TOTAL ECLIPSE. 



41 



and we have the exquisite spectacle of a total eclipse. 
The objects that I desire to mention particularly are 
the corona and the prominences. 





Fig. 18. — Total Eclipse of the Sun, May 6, 1883 (drawn 
by Trouvelot). 

A pretty picture of the total eclipse of the sun which 
occurred on May 6, 1883, is here shown (Fig. 18). It 



42 STAR-LAND. 

is taken from a drawing made by M. Trouvelot, who 
was sent out with a French observing party. They 
went a very long way to see an eclipse, but what they 
saw recompensed them for all their trouble. The track 
along which the phenomenon could be best seen lay in 
the Pacific Ocean, and a place had to be selected which 
was so situated that the sun should be high in the 
heavens at the important moment, and also that the 
duration while the total eclipse lasted should be as long 
as possible. They accordingly went to Caroline Island, 
and all this journey to the other side of the earth was 
taken to witness a phenomenon that only lasted five 
minutes and twenty-three seconds. Short though these 
precious minutes were, they were long enough to enable 
good work to be done. Careful preparations had been 
made so that not a moment should be thrown away. 
Each member of the party had his special duty allotted 
to him, and this had been rehearsed so carefully before- 
hand that when the long-expected moment of " totality " 
arrived there was neither haste nor confusion ; every 
one carefully went through his part of the programme. 
M. Trouvelot, for instance, occupied himself for two 
minutes and a few seconds in making the sketch that 
we now show. No doubt an accomplished astronomical 
artist like M. Trouvelot would gladly have taken longer 
time for his sketch of so unique a sight, but brevity was 
imperative. He had already had experience of similar 
eclipses, so that he was prepared at once to note what 
ought to be noted, and the picture we have shown is 
the result. This was completed within less than half 
of the duration of totality, and the artist had still three 



WATCHING AN ECLIPSE. 



43 



minutes left to devote to another and quite different 
part of the work, which does not concern us at present. 




Fig. 19. — The Corona of the Sun, 1882 (by Schuster). 

I want you particularly to look at these long branches 
or projections which we see surrounding the sun when 



44 STAR-LAND. 

totally eclipsed. They shine with a pearly light, and, 
in fact, it is stated that even during the gloomiest por- 
tion of the time there was still as much illumination as 
on a bright moonlight night. All that light came from 
this glorious halo round the sun which astronomers call 
the " corona." We do not under ordinary circumstances 
obtain even the slightest glimpse of this object. Even 
during a partial eclipse of the sun it is not visible, but 
directly the moon quite covers the sun, so as to cut off all 
the direct light, then the corona springs into visibility. 
It is always there, no doubt, though we cannot see it. 

One of the most interesting photographs of the 
eclipsed sun which has ever been taken was that by 
Professor Schuster in 1882 (Fig. 19). The corona is 
well shown, and also a comet. 

The other appendages to the sun ivhich can be 
seen during an eclipse are the objects which we call 
" prominences." They are of a ruddy color, and seem 
to be great flames, which leap upwards from the glow- 
ing surface of the sun below. Though the existence of 
the prominences was first discovered by their presence 
during eclipses, it fortunately happens that we are no 
longer wholly dependent on eclipses for the purpose of 
making our observations of these remarkable objects. 
It is true that we may look at the sun with even the 
biggest and most powerful telescope in the world, and 
still not be able to perceive anything of the promi- 
nences. We require the aid of a special appliance called 
the spectroscope to render them visible. But I am not 
now going to describe this ingenious contrivance. I am 
only going to speak of the results which have been 



SOLAR PROMINENCES. 45 

obtained by its means. We shall here again avail our- 
selves of the experience of M. Trouvelot for a picture 
of two of these wonderful appendages. 



Fig. 20. — Solar Prominences {drawn by Trouvelot). 

The view (Fig. 20) shows the ordinary aspect of the 
sun diversified with groups of dark spots. The fringe 
around the margin of the globe is of some ruddy mate- 
rial, forming the base of the flames which rise from the 
glowing surface. No doubt these flames are also often 



16 



STAB LAND, 



present on the face of the sun, but we cannot see them 
against the brilliant background. They are only per- 
ceptible when shown against the sky behind, At two 
points of this ruddy fringe, which happen curiously 
enough to be nearly opposite to each other, two colossal 
flames have burst forth. They extend to a vast dis- 
tance, which is quite one-third of the width of the sun. 
The vigor of these outbreaks may be estimated by the 
remarkable changes which are incessantly going on. 
These great flames may indeed be said to flicker; only, 
considering their size, we must allow them a little more 
time than is demanded for the movements of flames of 
ordinary dimensions, The great flame on the left was 
obviously declining in brilliancy when first scum. In a 
quarter of an hour it had broken up into fragments, 
some o( which were still to be scum floating in the 
sun's atmosphere. In ten minutes more the Light of 
this flame had almost entirely vanished, Surely these 
are changes o\' extraordinary rapidity when we remem- 
ber the size of this prominence, It was nearly 300,000 
miles in height that is to say, about thirty-seven 
times the width of our earth. 

Great as are these prominences, others have been 
recorded which are even Larger, One of them has 
boon soon to rush up with a speed of 200,000 miles 

an hour that is, with more than two hundred times 

the pace of the swiftest of rifle-bullets, 



NIGHT AND DAY. 
The sun is bright, and the earth is (lark. The sun 

gives Light ami boat, ami the earth receives light ami 



NIGHT AND DAY. 47 

heat. We should be in litter darkness were it not for 
the sun; at Least, all the Light we should have, beyond 
our trivial artificial Light, would come from the feeble 
twinkle of the stars. The moon would be no use, for 
the brightness of the moon is merely the reflection of 
the sunbeams. Were the sun's Light completely extin- 
guished we could never again see the moon, and we 
should also miss from the sky a few other bodies, which 
we call planets, such as Jupiter and Venus, Mars and 
Saturn. But the stars would he the same as before, for 
they do not depend upon the sun for their light. We 
shall, indeed, afterwards see that each star is itself a sun. 

Picture to yourself the earth as receiving a stream 
of sunbeams. These beams fall on one half of our 
globe, and give to it the brilliance of day. The other 
half of the earth of course receives no sunlight. It is 
in the shadow, and consequently the darkness of night 
there prevails. The boundary between light and dark- 
ness is not quite sharply defined, for the pleasant twi- 
light softens it a Little, SO that we pass gradually from 
day to night. Looking at the progress of the sun in 
the course of the day, we see that he rises far away in 
the east, then he gradually moves across the heavens 
past the south, and in the evening declines to the west, 
sets, and disappears. All through the night the sun is 
gradually moving round the opposite side of the earth, 
illuminating New Zealand and Japan and other remote 
countries, and then gradually working round to the 
east, where he starts afresh to give us a new day here. 

Our ancestors many ages ago did not know that 
the earth was round. They thought it was a great 



48 STAK-LAND. 

flat plain, and that it extended endlessly in every 
direction. They were, however, much puzzled about 
the sun. They could see from the coasts of France 
and Spain or Britain that the sun gradually disappeared 
in the ocean; they thought that it actually took a 
plunge into the sea. This would certainly quench the 
glowing sun; and some of the ancients used to think 
they heard the dreadful hissing noise when the great 
red-hot body dropped into the Atlantic. But there 
was here a difficulty. If the sun were to be chilled 
down every evening by dropping into the water 
hundreds of miles away to the west, how did it hap- 
pen that early the next morning he came up as fresh 
and as hot as ever, hundreds of miles away to the 
east? For this, indeed, it seemed hard to account. 
Some said that we had an entirely new sun every 
day. The gods started the sun far off in the east, and 
after having run its course it perished in the west. 
All the night the gods were busy preparing a new 
sun to be used on the succeeding day. But this 
was thought to be such a waste of good suns that a 
more economical theory was afterwards proposed. The 
ancients believed that the continents of the earth, so 
far as they knew them, were surrounded by a limit- 
less ocean. At the north, there were high mountains 
and ice and snow, which they thought prevented access 
to this ocean from civilized regions. Vulcan was the 
presiding deity who navigated those wastes of waters, 
and to him was intrusted the responsible duty of 
saving the sun from extinction. He had a great boat 
ready, so that when the sun was just dropping into 



HOW VULCAN MANAGED THE SUN. 49 

the ocean at sunset he caught it, and during all the 
night he paddled with his glorious cargo round by the 
north. The glow of the sun during the voyage could 
even be sometimes traced in summer over the great 
highlands to the north. This, at all events, was their 
Avay of accounting for the long midsummer twilight. 
After a tedious night's voyage Vulcan got round to 
the east in good time for sunrise. Then he shot the 
sun up with such terrific force that it would go 
across the whole sky, and then the industrious deity 
paddled back with all his might by the way he had 
come, so as to be ready to catch the sun in the even- 
ing, and thus repeat his never-ending task. 

THE DAILY ROTATION OF THE EARTH. 

Vulcan and his boat seemed a pretty way of account- 
ing for the sun's apparent motion. The chief drawback 
was that it was all work and no play for poor Vulcan. 
There were also a few other difficulties. Captains of 
ships told us that they had sailed out on the great sea, 
and that so far from finding that the ocean extended on 
and on in one flat plain forever, the water seemed to 
bend round, so that, in fact, after sailing far enough in 
the same direction, they found that they would be 
brought back again to the place from which they started. 
They also knew a little about the north. They told us 
that there could be no such ocean as that which Vulcan 
in this fable was supposed to navigate. It also appeared 
that ships had been voyaging all over the globe night 
and day in every direction, and that no captain had ever 



50 



STAR-LAND. 



seen the sun coming down to the sea, and still less had 
he ever met with Vulcan in the course of his incessant 
voyages. Thus it was discovered that the earth could 
not be a never-ending flat, but that it must be a globe, 
poised freely in space without any attachment to hold 
it up. It was thought that the change from day to 
night might be accounted for by supposing that the 




Fig. 21. — How we illustrate the Changes between Day and Night. 

sun actually went round the earth through the space 
underneath our feet. This is, indeed, what it seems to 
do. But there was a great difficulty about this expla- 
nation, which began to be perceived when the size 
and distance of the sun were considered. It required 
the sun to possess an alarming activity. He would 
actually have to rush round a circle one hundred and 



DAY AND NIGHT. 51 

eighty million miles in diameter and complete this 
astonishing voyage once every day. 

A little reflection will show that a very much simpler 
explanation was available. It w^as shown that the sun 
need not revolve round the earth once every day, but 
that everything would be explained if the earth itself 
turned round in such a way as to produce the changes 
from day to night. We may illustrate the case by this 
figure (Fig. 21). The small globe is the earth, which 
I can turn by the handle. The lamp will represent the 
sun, and, as at present shown, the side of the earth, on 
which England lies, is towards the lamp and in full day. 
On the opposite side of the globe are other countries 
such as New Zealand, and there it is dark. You see 
that by simply turning the handle I can move England 
gradually round so that it passes into the dark side, and 
then night falls over the country. At the same time 
New Zealand is turned round to enjoy the smiles of 
day. This is a very simple method of accounting for 
the succession of day and night, and it is also the true 
method. We have already seen that the sun turns 
round, and now we find that the earth also turns, but 
the little body, the earth, goes much the faster, for it 
makes twenty-five turns while the sun goes round 
once. 

Our earth is at this moment spinning round at a 
speed so great that London moves many hundreds of 
miles every hour. A town near the equator would 
gallop round at a pace of more than a thousand miles 
an hour — quicker, in fact, than a rifle-bullet. Don't 
you think that we ought to perceive that we are being 



52 STAR-LAND. 

whirled about in this terrific fashion ? We know that 
when we are flying along in a railway train, we feel the 
jolting and we hear the noise, and we feel the blast 
of air if we put our heads out of window, and we see 
the trees as they appear to rush past. All these things 
tell us that we are in rapid motion. But suppose these 
sensations were absent. Imagine a line so perfectly 
laid that no jolts are perceptible, and that no racket is 
heard ; draw down the blinds so that nothing can be 
seen, how then are we to know that we are moving? 
Indeed, your grandfathers used to be able to enjoy such 
a tranquil locomotion. I remember seeing in my child- 
hood the fly-boats, as they were called, on the Royal 
Canal, wherein passengers were conveyed from Dublin 
to the West of Ireland, before the railway was made. 
The fly-boat w r as a sort of Noah's ark in appearance, 
drawn by a horse cantering along the towing-path. In 
the cabin of such a vessel, where there was not the 
slightest motion of rolling or pitching — nothing but 
noiseless gliding along the canal — no one would be 
conscious of motion, so long as he did not look through 
the cabin windows. No one was ever seasick in a fly- 
boat ; it was the perfection of travelling for those who 
loved ease and quiet. 

The motion of the earth round its axis is, so far, like 
that of the fly-boat. It is so absolutely smooth that we 
do not feel anything, and we only become conscious of 
it by looking at outside objects. These are the sun, or 
the moon, or the stars. We see these bodies apparently 
going through their unvarying rising and setting, just 
as, in looking out from the fly-boat, the passengers in 



ROTATION OF THE EARTH. 53 

that quaint old conveyance could see the houses and 
trees as they passed. 

Seeing is believing ; and I should like here, in this 
very theatre, to show you that we are actually turning 
round ; and this I am enabled to do by the kindness of 
my distinguished friend, Professor Dewar. 

I am tempted to wish that I had Aladdin's lamp for 
the moment, for I would rub it, and when the great 
genie appeared, I would bid him take the Royal Insti- 
tution, and all of us here, to a place which everybody 
has heard of, and nobody has seen — I mean the North 
Pole. It would be so easy to describe the experiment 
I am about to show you, there. It is not so easy here. 
But it will be sufficiently accurate for our purpose to 
suppose that we actually have made the voyage, and 
that this is the Pole at the centre of the lecture-table. 
The direction of the axis round which the earth is 
turning is a line pointing up straight to the ceiling. 
This lecture-table and all the rest of the theatre is 
going round. In about six hours it will have moved 
a quarter of the way, and in twenty -four hours it will 
have gone completely round. That is, at least, what 
would happen if we were actually at the Pole. As we 
are not there, for the Pole is many miles away from the 
Royal Institution, I must slightly modify this statement, 
and say that the table here takes more than twenty-four 
hours to go round. And now I want some way of 
proving that such is actually the case. There is no use 
in our merely looking at it, because we ourselves, and 
this whole building, and the whole of London, are all 
turning together. What we want is something which 



54 



STAR-LAND. 



does not partake of the motion. Here is a heavy leaden 
ball (Fig. 22). It is fastened to the loof by a fine steel 
wire, and you see it swings to and fro with a deliberate 




and graceful motion. I want it to oscillate very 
steadily, so I draw it to one side and tie it by a piece 
of thread to a support, and then I burn the thread, and 
the great ball begins to swing to and fro. It would 
continue to do so for an hour, or indeed for several 



THE PENDULUM AND THE TABLE. 55 

hours, and it is a peculiarity of this motion that the 
vibration always remains in the same direction in space. 
Even the rotation of the earth will not affect the plane 
of this great pendulum, so far at least as our experiment 
is concerned. Here, then, we have a method of testing 
my assertion about the turning round of this theatre. 
I mark a line on the table, directly underneath the 
motion of the ball to and fro. If we could wait for an 
hour or so, we should see that the motion of the ball 
seemed to have altered to a direction inclined to its 
original position, but it is really the table that has 
moved, for the direction of the motion of the ball is 
unaltered. We cannot, however, wait so long, there- 
fore I show you the ingenious method which Professor 
Dewar has devised. By a beam from the electric light, 
he has succeeded in so magnifying the effect that even 
in a single minute it is quite obvious that the whole 
of this room is distinctly turning round, with respect 
to the oscillations of the pendulum. This celebrated 
experiment proves by actual inspection that the earth 
must be rotating. By measuring the motion we might 
even calculate the length of the day, though I do not 
say it would be an accurate method of doing so. 

The proper way of finding how long the earth takes 
to turn round is by observing the stars. Fix on any 
star you please, and note it in a certain position to-night ; 
if you then observe the moment when the star is in the 
same place to-morrow, the interval of time that has 
elapsed is the true duration of one complete rotation. 
When accurately measured its length is found to be 
23 hours 56 minutes 4 seconds, or about four minutes 



56 



STAR-LAND. 



shorter than the ordinary day, measured from one noon 
to the next. 



ANNUAL MOTION OF THE EARTH ROUND THE SUN. 

I have as yet only been speaking of the daily move- 
ments by which the 
sun appears to go 
across the heavens 
between morning 
and evening. We 
next consider the 
annual movements 
which give rise to 
the changes of the 
seasons. It is now 
Christmastide, when 
the days are short 
and dark, while six 
months ago the days 
were long and glori- 
ous in the warmth 
and brightness of 
summer. A similar 
recurrence of the 
seasons takes place 
every year, and thus 
we learn that some 
great changes alter 
the relation between 
the earth and the 
We must try and explain this. 




Fig. 23.- 



-The Changes of the Sun with 
the Seasons. 



sun year after year. 



THE SUN IN SUMMER AND WINTER. 57 

Why is it that we enjoy warmth at one season, and 
suffer from frost and snow at another ? 

Note first a great difference between the sun in sum- 
mer and the sun in winter. I will ask you to look out 
at noon any day when the clouds are absent, and you 
will then find the sun at the highest point it reaches 
during the day. All the morning the sun has been 
gradually climbing from the east ; all the afternoon it 
will be gradually sinking down to the west. Let us 
make the same observation at different parts of the 
year. Suppose we take the shortest day in December. 
You will look out about twelve o'clock from some situ- 
ation which affords a view towards the south, and there, 
as shown in the adjoining sketch (Fig. 23), is the mid- 
winter sun. 

But now the spring approaches, and the days begin 
to lengthen. If you watch the sun you will see it pass 
higher and higher every noon until Midsummer Day 
is reached, and then the sun at noon is found quite 
high up in the sky. As autumn draws near, the sun 
at noon creeps downwards again until, when the next 
shortest day has come round, we find that it passes just 
where it did at the previous midwinter. With unceas- 
ing regularity year after year the sun goes through 
these changes. When he is high at noon we have days 
both long and warm ; when he is low at noon we have 
days both short and cold. 

Vulcan with his golden boat was naturally expected 
to give an explanation of this. As the summer drew 
on, each day Vulcan shot out the sun with a stronger 
impulse, so that it should ascend higher and higher. 



58 



STAR-LAND. 



His greatest effort was made on Midsummer Day, when, 
after rowing but a little way round from the north 

towards the east, he 
drove off the sun with 
a terrific effort. The 
sun soared aloft to the 
utmost height it could 
reach, and in the mean- 
time Vulcan returned 
to the west to be ready 
to catch the sun as 
it descended. On the 
other hand, in mid- 
winter, he came round 
much further through 
the east to the south, 
and then shot up the 
sun with his feeblest 
effort, and had to 
paddle as hard as ever 
he could so as to com- 
plete his long return 
voyage during the brief 
day. 

It is evident that 
there are two quite 
distinct kinds of motion 
of the san. There is first the daily rising and 
setting, for which we have accounted by showing that 
it is merely an appearance produced by the fact that 
the earth is turning round. But now we have been 




Fig. 24. — How the Stars are to be seen 
in broad Daylight. 



STARS AS HELPERS. 59 

considering quite a different motion by which the sun 
seems to creep up and down in the heavens, and this 
takes a whole year to go through its changes. 

There is still another point which we must consider 
before we can understand all these puzzling movements 
of the sun. We shall ask the stars to help us by their 
familiar constellations. You know, perhaps, the Great 
Bear, or the Plough as it is often called, and Orion. 
There are also Aries the Ram, Taurus the Bull, and 
other fancifully named systems. These constellations 
have been known for countless ages, and for our pres- 
ent purposes we may think of them as permanent 
groups in the heavens, which do not alter either their 
own shapes or their positions relatively to each other. 
These groups of stars extend all around the sky. They 
are not only over our heads and on all sides down to 
the horizon, but if we could dig a deep hole through 
the earth, coming out somewhere near New Zealand, 
and if we then looked through, we should see that there 
was another vault of stars beneath us. We stand on 
our comparatively little earth in what seems the centre 
of this great universe of stars all around. It is true we 
do not often see the stars in broad daylight, but they 
are there nevertheless. The blaze of sunlight makes 
them invisible. A good telescope will always show the 
stars, and even without a telescope they can sometimes 
be seen in daylight in rather an odd way. If you can 
obtain a glimpse of the blue sky on a fine day from the 
bottom of a coal pit, stars are often visible. The top 
of the shaft is, however, generally obstructed by the 
machinery for hoisting up the coal, but the stars may 



60 STAR-LAND. 

be seen occasionally through the tall chimney attached 
to a manufactory when an opportune disuse of the 
chimney permits of the observation being made (Fig. 24). 
The fact is that the long tube has the effect of com- 
pletely screening from the eye the direct light of the 

Pisces 

^"'"September"^-^ 



/ 



/ 



/ 



.8/ 

I' I 

8I-3 

\ 




\ 



N ^-*^ March 
Virgo 

Fig. 25. — The Sun seems to revolve around the Earth. 

sun. The eye thus becomes more sensitive, and the 
feeble light from the stars can make its impression, and 
produce vision. From all these various lines of reason- 
ing we see that there can be no doubt of the continuous 
presence of stars above and around us, and below us, 
on every side, and at all times. 

If you look out at Christmas time, towards the south, 



FOUR USEFUL CONSTELLATIONS. 61 

you will see the Belt of Orion and the Dog Star in a 
splendid portion of the heavens. These stars you will 
see every winter in the same place. But you may look 
in vain for them in summer. No doubt you can see 
stars in the summer evenings, but they will be totally 
different from those that adorned the skies in winter. 
Each season has its own constellations. This simple 
fact was known to the ancients, and we shall find its 
explanation full of meaning. Let us select four well- 
known constellations which will best answer our pur- 
pose. They lie in a circle round the heavens. They 
are Orion, Virgo, Scorpio, and Pisces. I am supposing 
that you are looking out at midnight towards the south. 
In December you will see Orion ; in March, Virgo ; in 
June, Scorpio ; and in September, Pisces ; and then 
next December you will be looking at Orion again. 
See what this proves. At midnight, of course, the sun 
is at the other side of the earth, so that if I am looking 
at Orion in midwinter the sun must be behind my 
back. Look at our little picture (Fig. 25). The earth 
is in the middle, and the sun must be on the opposite 
side to Orion. That is, the sun must be somewhere 
about the position I have marked at A. In March we 
see Virgo in the south at midnight, when, of course, 
the sun is at the other side of the earth ; so that the 
sun must be somewhere at b. In June Scorpio is seen, 
so that the sun must be at the other side, at c. That 
is to say, in midsummer the sun is in that part of the 
sky where Orion is situated. If, therefore, on a bright 
June day we could see the stars, we should find Orion 
in the south. But, of course, the light of the sun 



62 STAR-LAND. 

makes Orion invisible. We can, however, see the stars 
by our telescopes, and on rare occasions an eclipse of 
the sun will occur, by which he is temporarily extin- 
guished, and then we can see the stars without the help 
of a telescope, even though it is daytime. 

Pisces 
^"-""September^-^ 



/ 



D \ 



ij o. s s» u |i| 

7 



/ 



/ 



\ 



y 



^ *■*<*._ March ~~'~ 

Virgo 

Fig. 26. — The Earth, however, really revolves around the Sun. 

Thus it would seem as if the sun were first at A 
and then at B, c, and D, and then began to go round 
again. I say it would seem as if the sun had these 
movements, and the ancients thought there was no 
doubt about the matter. Even after it was plain that 
the earth turned round on its axis so as to give the 
changes of day and night, it was still thought necessary 



WHAT ARE WE TO SAY? 63 

to suppose that the sun went round the earth once in 
the year, in order to explain how the changes in the 
stars during the different seasons were produced. 

Here is another case in which we must be careful to 
distinguish between what appears to be true and what 
is actually the case. Everything that we undoubtedly 
see would be just as well explained by supposing that 
the sun remained at rest, and that the earth revolved 
around it, as in Fig. 26. If, for instance, the earth 
were at A in midwinter, then the sun is on the oppo- 
site side to Orion, and of course at midnight we shall 
be able to see Orion. So in spring the earth is at B, 
and we see Virgo, and similarly in summer we have 
Scorpio, and in autumn Pisces. Thus all that is actu- 
ally visible could be fully accounted for by regarding 
the sun as fixed in the centre, and the earth as travel- 
ling round it from A to B, to c and to D respectively, 
and completing the journey in a twelvemonth. Which 
idea are we to adopt ? Shall we say that the earth goes 
round the sun, or the sun goes round the earth ? 

I remember an old college story, which I cannot help 
giving you at this place. It may serve to lighten what 
I fear you must otherwise have thought rather a tedious 
part of our subject. There were three students brought 
up for examination in astronomy, and they showed a 
lamentable ignorance of the subject, but the examiner, 
being a kind-hearted man, wished, if possible, to pass 
them ; and so he proposed to the three youths the very 
simplest question that he could think of. Accordingly, 
addressing the first student, he said : " Now tell me, 
does the earth go round the sun, or the sun go round 



64: STAK-LAND. 

the earth ? " " It is — the earth — goes round the sun." 
" What do you say? " he inquired, turning rather sud- 
denly on the next, who gasped out: " Oh, sir — of 
course — it is the sun goes round the earth." "What 
do you say?" he shouted at the third unhappy victim. 
" Oh, sir, it is — sometimes one way, sir, and sometimes 
the other!" 

But which is it? Well, we must remember that 
the earth is comparatively a very little body and the 
sun a very big one, so it is not at all surprising to learn 
that the earth goes round the sun, which remains, prac- 
tically speaking, at rest in the centre. Thus our great 
earth and all it contains are continually bound in what 
is very nearly a circular course round the great lumi- 
nary. You will find it instructive to work out this 
little sum. How fast is the earth moving, or how far 
do we go in a second? We are about 93,000,000 miles 
from the sun, and the great circle that we go round 
has a diameter twice as great as this — that is, about 
186,000,000 miles. The circumference of a circle is 
nearly three and one-seventh times its diameter, and 
accordingly the whole length of the voyage in the year 
is about 585,000,000 miles. This has to be accom- 
plished in 365 days, so that the daily run must be 
about 1,600,000 miles. We divide this by 24, to find 
the distance journeyed each hour, which we find to be 
about 67,000 miles; and we must divide this again by 
60 to find the length covered in a minute, and by 60 
again for the progress made each second. It is truly 
startling to find that, night and day, this great earth 
has to travel more than eighteen miles every second 



QUICK TRAVELLING. 65 

in order to get round its mighty path in the allotted 
time. 

I began this lecture about forty minutes ago, and 
I think from what I have said you will be able to 
calculate a result that will, I dare say, astonish you. 
In these forty minutes we have moved about 45,000 
miles. No doubt my lecture commenced in this hall, 
and in your presence ; but can I truly say I began it 
here ? Well, no ; I began it not here, but at a place 
45,000 miles away; but we have all been travelling 
together, and the journey has been so very smooth 
and free from all jolts, that we never thought any- 
thing about the motion. 

I am sure many of those to whom I am now 
speaking have read accounts of voyages in the Arctic 
regions. You have been told of the sufferings of the 
crews during the long winters, amid the ice and snow ; 
and you have heard how, during that dismal period, 
there is total darkness, for the sun never rises for 
weeks and months together. On the other hand, these 
northern regions often present a more cheerful picture. 
During midsummer, the long darkness of winter is 
atoned for by perpetual sunshine. At midnight there 
is still the full brilliance of day, and the sun, though 
low, no doubt, has not passed below the horizon. Even 
in the northerly parts of Europe we can see the mid- 
night sun. Lord Dufferin, in his delightful narrative 
of a cruise, entitled " Letters from High Latitudes," 
gives an interesting illustration of the perplexities 
arising from endless daylight. It appears that every- 
thing went on happily until the fatal moment when 



66 STAK-LAND. 

the yacht crossed the Arctic circle. Then it was that 
dire tribulation arose among the poultry. A fine cock 
was the cause of the trouble. Knowing his duty, he 
always liked to be particular about performing the 
important task of crowing at sunrise. This he could 
do regularly, so long as the yacht remained in rea- 
sonable latitudes, where the sun behaved properly. 
But when they crossed the Arctic circle, the cock was 
confronted with a wholly new experience. The sun 
never set in the evening, and consequently never had 
to rise in the morning. What was the distracted bird 
to do? He did everything. He burst into occasional 
fits of terrific crowing at all sorts of hours, then he 
gave up crowing altogether, but finding that did not 
mend matters, he took to crowing incessantly. Exhaus- 
tion was succeeded by delirium, and rather than live 
any longer in a universe where the sun was capable of 
pranks so heartless, the indignant fowl flung himself 
from the vessel and perished in the Arctic Ocean. 

THE CHANGES OF THE SEASONS. 

In the adjoining figure, I show a little sketch 
(Fig. 27), by which I try to explain the changes of 
the seasons. It exhibits four positions of the earth, 
one on each side of the sun. The left, A, represents 
the earth when summer gladdens the northern hemi- 
sphere; while the right, c, shows winter in the same 
region. You will see the two central lines which 
represent the axis about which the earth rotates. Of 
course, the earth has no visible axis. The line which 



THE NORTH POLE. 



67 



runs through the globe from the North to the South 

Pole is imaginary. 

It remains fixed in 

the earth, for we 

can prove in our 

observatories that 

the Pole does not 

shift its position to 

any considerable 

extent in the earth 

itself. In fact, if 

we could reach the 

North Pole and 

drive a peg into 

the ground year 

after year to mark 

the exact spot, we 

should find that 

the position of the 

Pole was sensibly 

the same. Does it 

not seem strange 

that we should be 

able to know so 

much about the 

Pole, though we 

have never been 

able to get there ; 

have never, in fact, 

been able to get 

within less than 400 miles of it ? I think you will be able 




68 STAR-LAND. 

to understand the point quite easily. The latitude of a 
place, as you know from your geography, is the number 
of degrees, and parts of a degree, between that place and 
the equator. In our observatories, we can determine 
this so accurately that the difference between the lati- 
tude of one side of a room and of the other side of the 
same room is quite perceptible. As we find that the 
latitudes of our observatories remain sensibly unchanged 
from year to year, we are certain that the Pole must 
remain in the same place. Indeed, if the Pole were to 
alter its position by the distance of a stone's throw, the 
careful watchers in many observatories would speedily 
detect the occurrence. 

And now I must direct your attention to some- 
thing apparently quite different. When the battle of 
Waterloo was fought, the great victory w T as won with 
the aid of the old-fashioned musket, a smooth-bore gun 
which was loaded at the muzzle with a good charge of 
powder, and then a round bullet was rammed down. 
" Brown Bess," as the musket was called, was a most 
efficient weapon at close quarters, and indeed at any 
distance when the bullet hit; but there was the diffi- 
culty. The round bullets, rushing up the tube and 
out into the air in a somewhat vague manner, had a 
habit of roaming about, which was quite incompatible 
with the accurate shooting of our modern rifles. 

One great improvement in small arms consisted in 
giving to the bullet a rapid rotation about an axis 
which is in the line of fire. This is what the rifle 
accomplishes. The grooves in the barrel of the rifle 
twist round, and though they only give half a com- 



ABOUT RIFLE-BULLETS. 69 

plete turn in the length of the barrel, yet the speed of 
the bullet is so great that when it flies off it is actually 
spinning with the tremendous velocity of about one 
hundred and fifty revolutions a second. Even with 
the old-fashioned round bullet, the rifling of the barrel 
effected great improvement in the accuracy of the 
shooting. The introduction of the elongated bullets 
was another great improvement, while the adaptation 
of breech-loading enabled a bullet to be used rather 
larger than that which could have been forced down 
the barrel, and thus it was insured that the grooves 
should bite into the bullet as it hurries past and 
impart the necessary spin. 

A body rapidly rotating about an axis has a tend- 
ency to preserve the direction of that axis, and power- 
fully resists any attempt to change it. Our earth is 
spinning in this fashion. It is true that the rotation 
is, in one sense, a slow one, for it requires almost an 
entire day for each rotation. But when we remem- 
ber the dimensions of our earth, we shall modify this 
notion. We have already stated that any place on the 
equator has to travel more than one thousand miles 
each hour in order to accomplish the journey within 
the required time. So far, therefore, the earth moves 
like a rifle-bullet, and the direction of its axis remains 
constant. 

In the course of the great voyage between summer 
and winter, the earth travels from one side of the sun 
to the opposite side, and in doing so it still continues 
to spin about an axis parallel to the original direction. 
See the consequences which follow. The sun illumi- 



70 STAR-LAND. 

nates half the earth, and in the left position in Fig. 27, 
representing summer, the North Pole is turned over 
towards the sun, and lies in the bright half of the earth. 
There LS continual day at the North Pole, and night is 
unknown there at this time of year, because the turn- 
ing of the earth about its axis will not bring the Pole 
nor the regions near the Pole into the dark hemisphere. 
Thus it is that the Arctic regions enjoy perpetual day 
at this season. Look now at the position of England 
when the northern hemisphere is tilted towards the sun, 
and is consequently enjoying the full splendor of mid- 
summer. As the earth turns round, England will grad- 
ually cross the boundary between light and shade, and 
will enter upon the darkened hemisphere. Then there 
will be night in England, but you will see from the 
figure that the day is much longer than the night, 
and hence it is that we enjoy the line long days in 
summer. 

We next look at a different scene six months later. 
The earth has reached the other side of the sun, but the 
axis has remained parallel to itself, consequently the 
North Pole is now inclined entirely away from the sun. 
The earth continues to turn round as before, but its 
movements do not bring the North Pole or the sur- 
rounding Arctic regions out of the dark hemisphere, 
and consequently the night must be unbroken in these 
dismal circumstances. The long continuous day which 
forms the Polar midsummer is dearly purchased by 
the gloom and cold of a winter in which there is no 
sun for many weeks in succession. Observe also the 
changed circumstances of England. In the course of 

o o 



SUNSHINE AT THE NORTH POLE. 71 

each twenty-four hours it lies much longer in the dark 
hair of the earth than in the bright, and consequently 
there is only a short day succeeded by a long night. 

SUNSHINE AT THE NORTH POLK. 

It is a privilege of astronomers to be able to predict 
events that will happen in thousands of years to come, 
and to describe things accurately though they never 
saw them, and though nobody else has ever seen them 
either. No one has ever yet got to the North Pole, but 
whenever they do, we are able to tell them much of 
what they will see there. We may leave it to Jules 
Verne to describe how the journey is to be made, and 
how the party are to be kept alive at the North 
Pole. I shall give a picture of the changes of the 
seasons, and of the appearance in the stars, as seen from 
(hence. 

We shall, therefore, prepare to make observations 
from that very particular spot on this earth — the North 
Pole. I suppose that eternal ice and snow abide there. 
I don't think it would be a pleasant residence. How- 
ever, we shall arrange to arrive on Midsummer Day, 
prepared to make a year's sojourn. The first question 
to be settled is the erection of the hut. In a cold 
country it is important to give the right aspect, and we 
are in the habit of saying that a southerly aspect is the 
best and warmest, while the north and the east are sug- 
gestive only of chills and discomfort. Hut what is a 
southerly aspect at the North Pole, or, rather, what is 
not a southerly aspect? Whatever way we look from 



72 STAR-LAND. 

the North Pole we are facing due south. There is 
no such thing as east or west; every way is the south- 
ward way. This is truly an odd part of the earth. 
The only other locality at all resembling it would be 
the South Pole, from which all directions would be 
north. 

The sun would be moving all through the day in a 
fashion utterly unlike its behavior in our latitudes. 
There would, of course, be no such thing as rising and 
setting. The sun would, indeed, at first seem neither 
to go any nearer to the horizon nor to rise any higher 
above it, but would simply go round and round the sky. 
Then it would gradually get lower and lower, moving 
round day after day in a sort of spiral, until at last it 
would get down so low that it would just graze the 
horizon, right round which it would circulate till half 
the sun was below, and then until the whole disk had 
disappeared. Even though the sun had now vanished, 
a twilight glow would for some time be continuous. 
It would seem to come from a source moving round and 
round below the horizon, then gradually the light would 
become fainter and fainter until at last the winter of 
utter and continuous blackness had set in. The first 
indications of the return of spring would be detected 
by a feeble glow near the horizon, which would seem 
to move round and round day after day. Then this 
glow would pass into a continuous dawn, gradually 
increasing until the sun's edge crept into visibility, and 
the great globe would at last begin to climb the heavens 
by its continual spiral until midsummer was reached, 
when the change would go on again as before. 



THE SUN HAS RIVALS. 73 

Our first excursion to the country of Star-land has 
now been taken, and we have naturally commenced by 
studying that sun to which we owe so much. But 
we shall have to learn that though our sun is of such 
vital importance to us, yet, in magnificence and size, he 
has many rivals among the host of stars. 



LECTURE II. 

THE MOON. 

The Phases of our Attendant, the Moon — The Size of the Moon — How 
Eclipses are produced — Effect of the Moon's Distance on its Appear- 
ance — A Talk about Telescopes — How the Telescope aids us in View- 
ing the Moon — Telescopic Views of the Lunar Scenery — On the Origin 
of the Lunar Craters — The Movements of the Moon — On the Possibility 
of Life in the Moon. 

THE PHASES OF OUR ATTENDANT, THE MOON. 

The first day of the week is related to the greatest 
body in the heavens — the sun — and accordingly we 
call that day Sun-day. The second day of the week is 
similarly called after the next most important celestial 
body — the moon — and though we do not actually say 
Moon-day, we do say Monday, which is very nearly the 
same. In French, too, we have lune for moon, and 
Lundi signifies our Monday. The other days of the 
week also have names derived from the heavens, but 
of these we shall speak hereafter. We are now going 
to talk about the moon. 

We can divide the objects in this room into two 
classes. There are the bright faces in front of me, and 
there are the bright electric lights above. The electric 
lights give light, and the faces receive it. I can see 
both lights and faces ; but I see the electric lamps by 
the light which they themselves give. I see the faces 
by the illumination which they have received from the 

74 



THE LIGHT OF THE MOON. 75 

electric lights. This is a very simple distinction, but it 
is a very important one in Star-land. Among all these 
bodies which glitter in the heavens there are some 
which shine by their own light, like the lamps. There 
are others only brilliant by reflected light, like the faces. 
It seems impossible for us to confuse the brightness of 
a pleasant face with the beam from a pretty lamp, but 
it is often not very easy to distinguish in the heavens 
between a body which shines by its own light and a 
body which merely shines by some other light reflected 
from it. I think many people would make great mis- 
takes if asked to point out which objects on the sky 
were really self-luminous and which objects were merely 
lighted up by other bodies. Astronomers themselves 
have been sometimes deceived in this way. 

The easiest example we can give of bodies so con- 
trasted is found in the case of the sun and the moon. 
Of course, as we .have already seen, the sun is the 
splendid source of light which it scatters all around. 
Some of that light falls on our earth to give us the 
glories of the day; some of the sunbeams fall on the 
moon, and though the moon has itself no more light 
than earth or stones, yet when exposed to a torrent of 
sunbeams, she enjoys a day as we do. One side of her 
is brilliantly lighted ; and this it is which renders our 
satellite visible. 

Hence we explain the marked contrast between the 
sun and the moon. The whole of the sun is always 
bright; while half of the moon is always in darkness. 
When the bright side of the moon is turned directly 
towards us, then, no doubt, we see a complete circle, 



76 



STAR-LAND. 



and we say the moon is full. On other occasions a 
portion only of the bright surface is directed to us, and 
thus are produced the beautiful crescents and semi- 
circles and other phases of the moon. 

A simple apparatus (illustrated in Fig. 28), will 
explain their various appearances. The large india- 
rubber ball there shown represents the moon, which I 




Fig. 28. — To show that the Moon is lighted by Sunbeams. 

shall illuminate by a beam from the electric light. 
The side of the ball turned towards the light is glowing 
brilliantly, and from the right side of the room you see 
nearly the whole of the bright side. To you the moon 
is nearly full. From the centre of the room you see 
the moon like a semicircle, and from the left it appears 
a thin crescent of light. I alter the position of the 
ball with respect to the lamp, and now you see the 
phases are quite changed. To those on my left our 
mimic moon is now full; to those on my right the 
moon is almost new, or is visible with only a slender 
crescent. From the centre of the room the quarter 
is visible as before. We can also show the same series 
of changes by a little contrivance of Figs. 29 and 30. 



THE PHASES OF THE MOON. 77 

Thus every phase of the moon (Fig. 31), from the 
thinnest beautiful crescent of light that you can just 
see low in the west after sunset up to the splendor of 
the full moon, can be completely accounted for by the 
different aspects of a globe, of which one-half is bril- 
liantly illuminated. 

We can now explain a beautiful phenomenon that 
you will see when the moon is still quite young. We 




Fig. 29. Fig. 30. 

The Phases of the Moon. 

fancifully describe the old moon as lying in the new 
moon's arms when we observe the faintly illuminated 
portion of the rest of that circle, of which a part is 
the brilliant crescent. This can only be explained by 
showing how some light has fallen on the shadowed 
side ; for nothing which is not itself a source of light 
can ever become visible unless illuminated by light 
from some other body. 

Let us suppose that there is a man on the moon who 
is looking at the earth. To him the earth will appear 
in the same way as the moon appears to us, only very 
much larger. At the time of new moon the bright side 
of the earth will be turned directly towards him, so that 
the man in the moon will see an earth nearly full, and 



78 



STAR-LAND. 



consequently pouring forth a large flood of light. Think 
of the brightest of all the bright moonlight nights you 
have ever seen on earth, and then think of a light which 
would be produced if you had thirteen moons, all as big 
and as bright as our full moon, shining together. How 
splendid the night would then be ! You would be able 

to read a book quite easily ! 
Well, that is the sort of 
illumination which the 
lunar man will enjoy under 
these circumstances ; all 
the features of his country 
will be brightly lighted up 
by the full earth. Of 
course, this earth-lighted 
side of the moon cannot 
be compared in brilliancy 
with the sun-lighted side, 
but the brightness will 
still be perceptible, so that when from the earth we 
look at the moon, we see this glow distributed all 
over the dark portion ; that is, we observe the feebly 
lighted globe clasped in the brilliant arms of the cres- 
cent. At a later phase the dark part of the moon 
entirely ceases to be visible, and this for a double 
reason : firstly, the bright side of the earth is then not 
so fully turned to the moon, and therefore the illumina- 
tion it receives from earth-shine is not so great; and, 
secondly, the increasing size of the sun-lighted part of 
the moon has such an augmented glow that the fainter 
light is overpowered by contrast. You must remember 




Fig. 31. — The Changes in the 
Moon. 



THE SIZE OF THE MOON. 79 

that more light does not always increase the number of 
things that can be seen. It has sometimes the opposite 
effect. Have we not already mentioned how the bright- 
ness of day makes the stars invisible ? The moon her- 
self, seen in full daylight, seems no brighter than a 
small particle of white cloud. 

THE SIZE OF THE MOON. 

It is not easy to answer the question which I am 
sometimes asked, "Is the moon very big?" I would 
meet that question by another, " Is a cat a big animal ? " 
The fact is, there is no such thing as absolute bigness 
or smallness. The cat is no doubt a small animal 
when compared with the tiger, but I think a mouse 
would probably tell you that the cat was quite a 
big animal — rather too big, indeed, in the mouse's 
opinion. And the tiger himself is small compared with 
an elephant, while the mouse is large as compared 
with a fly. 

When we talk of the bigness or the smallness of a 
body, we must always consider what we are going to 
compare it with. It is natural in speaking of the moon 
to compare it with our own globe, and then we can say 
that the moon is a small body. 

The relative sizes of the earth and the moon may be 
illustrated by objects of very much smaller dimensions. 
Both a tennis ball and a football are no doubt familiar 
objects to everybody. If the earth be represented by 
the football, then the moon would be about as large as 
the lawn-tennis ball. But this proportion is not quite 



80 STAR-LAND. 

accurate, so I will suggest to you an instructive way of 
making a better pair of models of the earth and the 
moon. In fact, experiments somewhat similar to those 
I describe have been actually going on in every kitchen 
in the land during this festive season. For have not 
globes and balls of all sorts and sizes been made of 
plum-pudding, and it will only require a little care on 
the part of the cook to make a pair of luscious spheres 




Fig. 32. — Relative Sizes of the Earth and Moon. 

that shall fairly set forth the sizes of the earth and the 
moon. There is first to be a nice little round plum- 
pudding, three inches in diameter. It is just a little 
bigger than a cricket ball. It should, however, only 
make its appearance at a bachelor's table. Were it set 
down before a hearty circle on Christmas Day, dire dis- 
appointment would result. One boy of sound consti- 
tution could eat it all. Perhaps it would weigh about 
three-quarters of a pound. This little globe is to rep- 
resent the moon. 

Another plum-pudding is to be constructed which 



OUR PLUM-PUDDINGS. 81 

shall represent the earth (Fig. 32). We must, however, 
beg the cook to observe the proportions. The width of 
the earth, or the diameter, to use the proper word, is 
about four times the diameter of the moon. Hence, as 
the small plum-pudding was three inches across, the 
large one must have a diameter of twelve inches. This 
will be a family pudding of truly satisfactory dimen- 
sions ; perhaps the cook will be a little surprised to 
find the alarming quantity of materials that will be 
required to complete a sphere of plum-pudding a foot 
in diameter. 

These models having been duly made, and boiled, 
and placed on the table, we are now to propose the fol- 
lowing problem : — 

" If one schoolboy could eat the small plum-pudding, 
how many boys would be required to dispose of the 
large one ? " 

The hasty person, who does not reflect, will at once 
dash out the answer, "Four!" He will say, "It is 
quite plain that, since one of the puddings has four 
times the diameter of the other, it must be four times 
as big ; and therefore, as one boy is able to eat the 
small pudding, four boys will be adequate for the large 
one." But the hasty person will, as usual, be quite 
wrong. His argument would be sound if it were merely 
two pieces of sugar-stick that he was comparing ; no 
doubt there is only four times as much material in a 
piece twelve inches long as there is in a piece three 
inches long. But the plum-puddings have breadth and 
depth, which are in the same proportions as the length, 
and the consequence is that the large plum-pudding is 



82 STAR-LAND, 

far more than four times as big as the small one. No 
four boys, however admirable their capacities, would be 
equal to the task of consuming it. Nor even it' four 
more boys were called in to help would the disli be 
cleared. Twenty boys, forty boys, fifty boys would not 
be enough. It would take sixty-four boys to demolish 
the magnificent plum-pudding one foot in diameter. 

If the cook will try the experiment, she will find that 
by taking the materials sufficient for sixty-four small 
plum-puddings all o( the same size, and 110x1110' them 
together, she will, no doubt, make a large plum- 
pudding, but its diameter will only be four times that 
of the small puddings. 

As a matter of fact, the moon is 2160 miles in 
diameter, and the earth is 7918 miles. These numbers 
are xo nearly 2000 and 8000 respectively, that for sim- 
plicity I have spoken of the earth as haying a diameter 
four times as great as the moon. If we want to be very 
accurate, we ought to determine the ratio of the two 
quantities from the figures just given. Our illustration 
of the plum-puddings must, therefore, be a little modi- 
fied. The earth is not quite so much as sixty-four 
times as big as the moon ; but this figure is sufficiently 
accurate for our present purpose. 

Another interesting question may be proposed, 
namely : How much land is there on the moon? We 
might state the answer in acres or in square miles ; 
but it will, perhaps, be more instructive to make a 
comparison between the moon and the earth. 

Here also I shall use an illustration; and we shall 
again consider two globes Ayhieh are respectively three 



COMPARISON OF WEIGHTS. 83 

inches and twelve inches in diameter. The globes I 
use this time are hollow balls of india-rubber. These 
will represent the earth and the moon with sufficient 
accuracy, and the relative surfaces of these two globes 
is what I want to find. There are different ways in 
which the comparison might be made. I might, for 
instance, paint the two globes and see the quantity of 
paint that each requires. If I did this, I should find 
that the great globe took just sixteen times as much 
paint as the small one. We can adopt a simpler plan. 
The india-rubber in one of these balls has the same 
thickness as in the other, as they are each hollow, so 
that the quantity which is required for each ball may 
be taken to represent its surface. By simply weighing 
the two balls, I perceive that the large one is sixteen 
times as heavy as the small one. You notice here the 
difference between the comparative weights of two hol- 
low balls and two solid ones of the same material. 
Had these globes been of solid india-rubber, the large 
one would have weighed sixty-four times as much as 
the small one, just as in the case of the plum-puddings ; 
but being hollow, the ratio of their Aveights is only the 
square of the ratio of their diameters — that is to say, 
four times four, or sixteen. 

We are thus taught that if the moon w^ere exactly 
one-fourth of the diameter of the earth, its surface 
would be one-sixteenth part of that of the earth. It 
would, no doubt, have made our subject a little easier 
and simpler if the moon had been created somewhat 
smaller than it is. As, however, the universe has not 
been solely constructed for the purpose of these talks 



84 STAR LAND. 

about Star-land, wo must take things as wo find them. 
This proportion is not tour ; it is more nearly 3$, and 
the relative surfaces of the two bodies is the square of 
U-, or about 1 o.\. In other words, the entire extent of 
the surface of our globe is about thirteen and a half 
times that of the moon. 

The face of the full moon, being half the entire extent. 
of the surface, is, therefore, about one-twenty-seventh 
part of the earth's surface — continents, oceans, seas, 
and islands all taken together. The British Empire 
and the Russian Empire are each of them as Large as 
the face of the full moon. 

HOW ECLIPSES ARE PRODUCED. 

Tho moon is the attendant, or the satellite of the 
earth, ministering to the wants of the earth by mitigat- 
ing the darkness (^ our nights. The earth goes around 

the sun in its annual journey of 365 days. The moon 

revolves around tho earth once every twenty-seven 

days. The motion of the moon is thus a, very compli- 
cated One, for it is, in fact, moving round a body which 
is itself in constant motion (Fig. 33). 

You will sec by your almanacs every year that certain 
eclipses are to take place ; and after what we have said 
about the sun and the moon, it will be easy to under- 
stand how eclipses arise. There are two different kinds. 
Von will sometimes see an eclipse of the moon, and 
sometimes those eclipses of the sun of which we have 
spoken in the last Lecture. Von may be surprised to 
find with what accuracy the eclipses can be predicted. 



ECLIPSES. 85 

We can tell not only those that will occur this year and 
next year, but we could also foretell the eclipses that 
will appear in a hundred or a thousand years to come ; 
or we can, with equal ease, calculate backwards, so as 



Fig. 33. — To show how the Earth goes round the Sun and the Moon 
round the Earth. 

to find the circumstances of eclipses that happened 
thousands of years ago. This shows how well Ave have 
learned the way the moon moves. 

An eclipse of the sun is the simpler occurrence, so 
we shall describe it first. It happens when the moon 
comes between the earth and the sun. Look at our 
little astronomers shown in Fig. 34. A boy and a girl 
are both gazing at the sun, when the moon comes be- 
tween. To the boy the moon appears to take a great 
bite out of the sun, so that it looks like the left-hand 



86 



STAB LAND, 



picture m Fig. 85. ^1 have drawn a lino from the end 
of the telescope in Fig, 84, which shows how much of 



\ 




Moon • 




\ \ 






;' Pi*» 



Kic. 34, a Total Eclipse to the Girl and a Partial Eclipse t« 
the Boy, 




the sun is cut off.) This would he railed a partial 
eel ipse of the sun. The almanac will sometimes de- 

soribe the eclipses as visible in London, or visible at 



TOTAL ECLIPSES. 



87 



Greenwich; l>u( that need not be taken so Literally as 
was supposed by a Kensington gentleman, who, on 
noticing thai the almanac said an eclipse was to be 

visible in London, called a cab and drove into the city 
to look for it. His almanac had not mentioned that it 
would be visible from his own house. Von may usually 
take for granted that when an eclipse is said to be 
visible from London or Greenwich, it will be more or 
Less visible all over England. Most of these eclipses 




Partial. Annular. 

Pig. 35. — Different Kinds of Solar Eclipse. 

are only partial, and though thev are interesting to 
Watch thev do not teaeh US mneh. By tar the most 

wonderful kind of eclipse is that in which the whole of 
the bright part of the sun is blotted out. Then, indeed. 
We do see wonders. But such eelipses are rare, and 

even when they do occur they only last a very few min- 
utes. The sights that are displayed are so interesting 



88 STAB LAND, 

that astronomers often travel thousands of miles to 
reach a suitable Locality for making observations. 

The girl in Fig, 34 is placed in the best possible 
position for seeing the eclipse. There you find heir 

right in the line o( the sun and moon : and 1 think 

you will agree that she cannot see any part of the sun, 
for the moon Is altogether in the way, 1 have drawn 
two dotted lines, one at each side. All that she can 
see beyond the moon must lie outside these dotted 
lines, and she will be in the dark as long as the moon 
stays in the way, AN' hen the eclipse is complete, com- 
parative darkness steals over the land. The birds are 
deceived, and fly home to the trees to roost. The owls 
and the bats, thinking their time has arrived, venture 
forth on their nocturnal business. Kvon flowers elose 
their petals, only to open a few minutes later when the 
sun again bursts forth. Other flowers that give forth 
their fragrance at night are also sweetly perceptible so 
long as the sun remains obscured. An unruly COW, 
accustomed to break into a meadow at night, was found 
there after an eclipse was over ; while 1 learn from the 
same authority that a man rushed over in great excite- 
ment to see what his chickens were doing, but came 
back much disappointed on finding them pecking away 
as if nothing had happened. 

It will sometimes happen that the moon is so placed 
that the edge of the sun can be seen all round it. A 
ease of the kind is shown in the right-hand picture of 
Fig, 35. It is called an annular, or ring-shaped eclipse. 

The eclipses of which we have been speaking are, of 
course, only to be seen during the day when the sun 



ECLIPSES OF THE MOON. 89 

must be up. The lunar eclipses, which are visible at 
night, are due to the Interposition of the earth between 
the sun and the moon. The sun is at night-time under 
our feet at the other side of the earth, and the earth 
throws a Long shadow upwards. If the moon enter 
into this shadow, it is plain that the sunlight is partly 
01 wholly cut off, and since the moon shines by no light 
of her own, but only by light borrowed from the sun, 
it follows that when she is buried in the shadow all the 
direct light is intercepted, and she must lose her bril- 
liancy. Thus we obtain what is called a lunar eclipse. It 
is total if the moon be entirely in the shadow. The eclipse 
is partial if the moon be only partly in the shadow. The 
lunar eclipse is visible to everybody on the dark hemi- 
sphere of the earth if the clouds will keep out of the way, 
so that usually a great many more people can see a lunar 
eclipse than a solar eclipse, which is only visible from a 
limited part of the earth. It thus happens that the lunar 
eclipse is the more familiar spectacle of the two. 

When the moon is entirely in the shadow, one might 
naturally think that it would become totally invisible. 
This is not always the case. It is a curious fact that 
in the depth of a total eclipse the moon is often still 
visible, for she glows with a copper-colored light, which 
is bright enough to render some of the chief marks on 
her surface distinctly discernible. 

EFFECT OF THE MOON'S DISTANCE ON ITS APPEARANCE. 

We are now about to take a good look at the moon 
and examine the different objects which are marked 



90 



STAR I.AM' 



upon it. There is a peouliar interest attached to this 
particular orb, because it is much the nearest of all the 
heavenly bodies to our globe, and therefore the cue that 
wo ran see the best, L£yery other object sun, star, 
or planet is hundreds, or perhaps thousands, of times 
as far off as the moon, It is right that we should desire 
to Learn all we ran about the bodies in space, We 

know that tin 1 earth is a great hall, and we see that 

there are mam other suoh bodies* Some of them air 
much Larger, and some of them art 1 smaller than the 
globe on which we dwell : some of them arc dark 
bodies Like the earth, and among them the moon is 
one. Is it not reasonable that we should make special 
efforts to find out all we can about this interesting 
neighbor ? 

Though the moon is so close 1 to us relali\cl\ to Other 

objects in space, yet when we express its distance in 
the ordinary methods el measurement it is a verv Long 
way off about 240,000 miles a Length nearly as 

great as that i>( all the railways in the world put 
together, An express train which runs forty miles an 
hour would travel 240 miles in Six hours, and tin 1 
whole distance to the moon would hi 1 accomplished in 
6000 hours, se> that travelling b\ nudit and day in 
eessanlh yOU would accomplish tlu 1 journey m 250 

days, To take another illustration, if you wrapped a 
thread ten times round the equator of the earth, it 
would hi 1 Long enough to stretch from the earth to the 
moon. Or suppose a cannon could be made sufficient 1 \ 
strong to be fired with a report Loud enough to be 
audible 240*000 miles away. The sound would onli 



THE DISTANCE OF THE MOON PROM US. 



91 



be heard ;ii that distance a fortnight after the d is<*Ji;ir<_»(; 
had taken place. 

The moon is too far for us to examine the particular 
features on its surfaee by the unaided eye. Suppose 
that there was a mighty city like London on the moon, 
with great buildings and teeming millions of people, 
and you went out on a line night to take a look at our 
neighbor. What d.0 you think you would be able to 
see of the great lunar metropolis? Would you be able 
to see its streets lull of omnibuses, or even its great 
buildings? Would you see St. PauTs and Westminster 
the great parks and the river? Of all these things 
your unaided eye would show you almost nothing. I 
call give you a little illustration. Suppose that you 
made a tiny model of London; imagine this little 
structure all complete, so thai the streets, the .build- 
ings, the bridges, the railways, the parks, and the 
Thames were placed in their true proportions; sup- 
pose that the miniature city was so small that it could 
stand on a penny postage stamp, surely everything 
would look very insignificant, even if you had the 

model in your hand and looked at it with the aid of 
a magnifying glass. But suppose it were put on the 
Other side of the table or on the other side of the room, 
or the other side of the street. Kven St. Paul's Cathe- 
dral itself would have ceased to be distinguishable; 
but yet the distance is not nearly great enough. Y on 

would have to put the little model a quarter of a mile 
away before it would be in the right position to illus- 
trate the appearance of a Lunar London to the unaided 
eve. 



92 STAR-LAND, 

A TALK ABOUT TELESCOPES. 

The astronomer will not be contented with a mere 
naked-eye inspection of a world so interesting as the 

moon. He will get a telescope to Help his vision. 
The word " telescope " moans a contrivance for look- 
ing at objects which are a long way off. We have 
explained that the further an object is, the smaller it 
appears to be. The telescope enables us to largely 
overcome this inconvenience. It has the effect of 
making a distant object look larger. 

'There are great differences in the forms of tele- 
scopes; and some instruments are large and some 
small, according to the purposes for which they are 
required. Perhaps the most useful practical applica- 
tion of the telescope is by the officer on duty on 
board a ship, lie is generally provided with a pair 
of these instruments bound together to form the 
" binocular." 

Von are all acquainted with this useful contrivance, 
or at all events with the opera-glass, that is used for 

purposes with which Landsmen are more familiar. The 
ship's telescope, or the binocular, or the opera-glass, 
is feeble in power when compared with the great 
instruments of the Observatory. The officer on the 

ship will generally be satisfied with a telescope which 
shall show the objects with which he is concerned 
at about one-third of their actual distance 4 . Inns, 
suppose his attention is directed to a great steamer 
three miles away, he wishes to see her more clearly, 
and accordingly he takes a view through his binocular. 



TELESCOPES. 93 

Immediately the vessel is so transformed that it seems 
to be only one mile away. The apparent dimensions 
of the object are increased threefold. The hull is 
three times as long, the masts and the funnel are 
three times as high, the sailors are three times as 
tall; various objects on the ship too small to be 
seen at three miles would be visible from one mile, 
and to that apparent distance the ship has now been 
brought. 

If the sailor desires to reduce the apparent distance 
of objects, how much more keenly does the astronomer 
feel the same want? At best, the sailor only has to 
scan a range of a few miles with his glass, but what 
are a few miles to the astronomer ? It is true that he 
can count the distance of the moon by thousands of 
miles, a good many thousands, no doubt, but for all 
other objects he must use millions, while for most 
bodies in space, millions of millions of miles are the 
figures we are constrained to employ. Need it be 
said that the astronomer must resort to every device 
he can to make the body appear closer. He does 
not despise the modest binocular. It is often a useful 
instrument in the Observatory. It gives most beau- 
tiful pictures of the celestial sceneiy, and you Avould 
be amazed to find how many thousands of stars you 
can see with its help which your unaided eye would 
not show you at all. The binocular will also greatly 
improve the appearance of the moon, but still its 
powers fall far short of what we require for the 
study of lunar landscapes. Even though we can 
reduce the moon's apparent distance to one-third its 



94 



STAR-LAND. 




Fig. 36. — The Dome at Dunsiuk Observatory. 



actual amount, yet still that third is a very consid- 
erable distance. One-third of 240,000 is 80,000, so 
that we can see the moon no better with a binocular 



A CONVENIENT INSTRUMENT. 



95 



than Ave should see it were it 80,000 miles away, and 
were we viewing it with the unaided eye. 

I am not going to enter here upon any detailed 
account of the telescope, because I shall say a little 




Fig. 37. — The Equatorial at Dunsink Observatory. 

more on the subject in a later lecture; at present 1 
only describe that form of instrument which is most 
convenient for studying the moon. I take as an illus- 
tration the South Equatorial at Dunsink Observatory, 
which belongs to Trinity College, Dublin. 



96 STAB LAM). 

This telescope has a building bo itself, which stands 
on the lawn in front of the house. The site is open 
and elevated, so as to command an extensive prospect 
of the heavens. You will see in Fig, 36 a picture of 
the structure. It is circular in form and is entered 
by the little porch. The most peculiar feature of an 
edifice intended to contain this kind of telescope is 
its roof, or Dome, as we eall it. It is of a hemi- 
spherical shape with a projecting rim at the bottom. 
Hut no one would go to the trouble and expense of 
making- a. round dome like that over the Observatory 

if it were not necessary for a particular purpose. The 
dome is very unlike ordinary roofs, not only in appear- 
ance, but also because it can turn round. In the next 
figure you will see a. section through the building, and 
the wheels are exposed by which the dome is carried, 
These wheels run easily on rails, so that when the 
attendant pulls the rope which you see in his hands, 
he turns round a, Large pulley, and that operates a little 
cogwheel which works into a rack, and thus makes the 
dome revolve. The roof is built o( timber, covered 

with copper; it weighs more than six tons, but the 

machinery is so nicely adjusted, that a child four years 

old can easily set the whole in motion. The object of 

all this machinery is seen when we learn that there is 
only one opening in the dome. It is covered by the 
shutter shown over the doorway in lug. 86, When 
opened to the top, it gives a long and wide aperture, 
through which the astronomer can look out at the 
heavens. Of course the dome has to be turned until 

the opening has been brought to face the required 



IHNSINK OBSERVATORY. 97 

aspect. The big telescope can thus be directed to any 
object above the horizon. You see a gentleman using 
the telescope (Fig. 37), and this shows that the great 
instrument is nearly three times as long- as the astron- 
omer himself ! No doubt the telescope seems to be 
composed of a good many different parts, but the 
essential portions o( the instrument are comparatively 
few and simple. At the upper end is the object glass, 
which consists of two Lenses, one of flint glass and the 
other of crown glass. Both of these must be of excep- 
tional purity, and the shape to be given to the lenses 
is a, matter of the utmost importance. It is in the 
making of this pair of glasses that the skill of the 
optician has to be specially put forth. So valuable 
indeed is an object glass which fulfils all the require- 
ments, that it is by far the most costly part of the 
instrument. There are no glasses in the interior of 
the tube until you come to the (Mid where the observer 
is looking iti. This is closed by an eyepiece consist- 
ing o( a lens, or a pair o( lenses. There are usually 
many different eyepieces for a telescope, and they 
contain lenses o( varied powers, to be used according 
to the state of the atmosphere, or to the particular 
kinds of observation in progress. 

If you point a big telescope to the sky, and see 
therein the sun or the moon or any of the stars, you 
will speedily find that the objects pass away out of 
view. Remember our earth is constantly turning 
round, and bears, o( course, the Observatory with it, so 
that though the telescope be rightly pointed to the 
heavens at one moment, bv the next it will have oeen 



98 STAR-LAND. 

turned aside. To you who are using the telescope, the 
appearance produced is as if the heavenly bodies were 
themselves moving. We can counteract this incon- 
venience. The telescope is supported on a pedestal, 
which is built on masonry, that goes down through the 
floor to its foundation on the solid rock beneath. In 
the iron casing at the top of the pedestal you will see 
a little window, and inside is clockwork driven by a 
heavy weight. This clockwork turns the whole tele- 
scope round in the opposite direction to that in which 
the earth is moving. The consequence is that the 
telescope remains constantly pointed to the same part 
of the heavens. 

This instrument is no doubt a large one, but of 
late years many much greater have been built. The 
most powerful telescope that has ever been erected is 
the great Yerkes instrument belonging to the University 
of Chicago, of which a picture is shown in Fig. 38. 
The object glass is 40 inches across. 

HOW THE TELESCOPE AIDS US IN VIEWING THE MOON. 

Those who are in charge of an observatory are often 
visited by persons who, coming to see the wonders of 
the heavens, and finding instruments of such great pro- 
portions', not unnaturally expect the views they are to 
obtain of the celestial bodies shall be of corresponding 
magnificence. So they are, no doubt, but then it fre- 
quently happens that the pictures which even the great- 
est telescope can display will fall far short of the ideal 
pictures which the visitors have conjured up in their 



THE YERKES TELESCOPE. 



99 




Fig. 38. — The Yerkes Telescope, University of Chicago. 



LOO 



sr.vi; LAND, 



own imaginations) so thai they are often sadly disap- 
pointed, Especially is this true with regard to the 
moon. 1 have seen people who, when they had a view 
of the moon through a great telescope, were surprised 
not to find Nasi ranges of mountains whioh Looked to 
them as bi^ as the Alps, or mighty deserts, over whioh 
the eye could roam for thousands of miles. They have 
sometimes expeoted to behold stupendous volcanoes that 
not only were, but that Looked to be as big as Vesuvius. 
Others seem to have thought they ought to see the 
moon with such olearness that the fields were to be 
quite visible, and somo would not have been muoh 
astonished it' they Had observed houses and Farmyards, 
and, perhaps, even oooks and hens. 

There arc 4 different ways ^( estimating the apparent 
dimensions o( an object, but tin 4 size the moon appears 
to me to have in a great telescope may be illustrated 
by taking an orange in your hand and Looking at the 
innumerable Little marks and spots mi its surface. The 
amount of detail that the eve will show on the orange 

is about equal to the amount of detail that a jmhhI 

telesoope will show on the moon. A desert on the 

moon, which really is a hundred miles across, will 
then correspond to a mark about an eighth of an inch 

in diameter on the orange. Some of von may ask what 
is gained by the use of a telesoope, for the moon Looks 

to ns as Large as a plate with the unaided eye, and now 

we hear it only Looks as big as an orange in the telesoope, 
Hut where is the plate with which vou compare your 
moon supposed to be held? It is surely not in your 

hand. It is imagined to be up in the sky, a very Long 



THE USE OF THE TELESCOPE. 



101 



way off. Though an orange is much smaller than a 
plate, yet you will he able to see many more details in 
the orange by taking it in your hand than you could 
see on a plate which was at the other side of the street. 




Fig. 39. — The Advantage of using a Telescope. 

I sometimes find that people will not believe how 
much the telescope that they are using is magnifying 
the moon until they use both eyes together, of which 
one is applied to the telescope, while the other is 
directed to the moon. It will then be seen, even with a 
very small instrument, that the telescopic moon is as big 
as the larger of the two crescents in the adjoining figure 
(Fig. 39), while the naked-eye moon is like the smaller. 



102 STAB LAND. 

The greatest telescopes arc capable of reducing the 
apparent distance of an object to about one-thousandth 

part of its actual amount. If, therefore, a body were 
a thousand miles away, it would, when viewed by one 
of these mighty instruments, be seen as Large as our 
unaided vision would show it, were the body only a 
single mile distant. No doubt this is a Large accession 
to our power, but it often falls far short o( what the 
astronomer would desire. The distances o( the stars 
are all so great that even when divided by one thou- 
sand, they are still enormous. If you have a number 
expressed by 100,000,000,000,000, then dividing it by 
a thousand merely means taking off three of the ciphers, 
and there is still a Large number left. We are, however, 
at present concerned with the moon, and, as its distance 
is about 240,000 miles, the effect of the best telescope 
is to reduce this distance apparently to 240 miles. 
Here, then, we find a limit to what the best o( all tele- 
scopes can do. It can never show us the moon better 
than, hardly indeed so well as, wo could see it with our 
unaided eye were it only 240 miles over our heads. 
We cannot expect the most powerful instruments to 
reveal any object on the moon unless that object were 
bio- enough to be stHMi by the unaided eye when '2 40 
miles away. What could we expect toseeat a distance 
o( 240 miles? 

Here is a little experiment which I made to study 
this point. I marked a round black dot on a sheet o( 
white paper. The dot was a quarter of an inch in diam- 
eter, and then I fastened this on a door in the garden, 
and walked backwards until the dot ceased to be visible. 



WHAT WE CAN SEE ON THE MOON. 103 

I found this distance to be about thirty-six yards. I 
tried a little boy of eight years old, and it appeared 
that the dot became invisible to him about the same 
time as it did to me. " What has this to do with the 
moon?" you will say. Well, we shall soon see. In 
thirty-six yards there are 5184 quarters of an inch, 
and as it is unnecessary to be very particular about the 
figures, we may say, in round numbers, that the distance 
when we ceased to be able to distinguish the dot was 
about five thousand times as great as the width of the 
dot itself. You need not, therefore, expect to see any- 
thing on the moon or on anything else which is not at 
least as wide as the five-thousandth part of the distance 
from which we are viewing it. The great telescope 
practically places the moon at a distance of 240 miles, 
and the five-thousandth part of that is about eighty 
yards ; consequently a round object on the moon about 
eighty yards in diameter would be just glimpsed as the 
merest dot in the most powerful telescope. To attract 
attention, a lunar object should be much larger than 
this. If St. Paul's Cathedral stood on a lunar plain, 
it would be visible in our great telescopes. It is 
true that we could not see any details. We should 
not be able to distinguish between a Cathedral and 
a Town-hall. There would just be something visible, 
so that the artist who was making a sketch of that 
part would put down a mark with his pencil to show 
that something was there. This will show us that 
we need not expect to see objects on the moon, even 
with the mightiest of telescopes, unless they are of 
great size. 



104 STAR-LAND. 

TELESCOPIC VIEWS OF LUNAR SCENERY. 

I have already warned you not to expect too much, 
even with the biggest of telescopes ; and just as a 
caution, I may, perhaps, tell you a story I once heard 
of an astronomer who had a great telescope. It was 
a very famous instrument, and people often came to 
the Observatory at night to enjoy a look at the heavens. 
Sometimes these visitors were grave philosophers, but 
frequently they were not very accomplished men of 
science. One evening such a visitor came to the 
Observatory, and sent in his name and an introduction 
to the astronomer, with a request that he might enter 
the temple of mystery. The astronomer courteously 
welcomed the stranger, and asked him what he specially 
desired to see. 

" Oh ! " said the visitor, " I have specially come to 
see the moon — that is the object I am particularly 
interested about." 

"But," said the astronomer, "my dear sir, I would 
show you the moon with pleasure, if you were here at 
the proper time ; but what brings you here now? Look 
up ; the evening is fine. There are the stars shining 
brightly, but where is the moon? You see it is 
not up at present. In fact, it won't rise till about 
half-past two to-morrow morning, and it is only 
nine o'clock now. Come back again in five or six 
hours, and you shall observe the moon with the great 
telescope." 

But the visitor evidently thought the astronomer 
was merely trying to get rid of him by a pretext. And 



THE GEOGRAPHY OE THE MOON. 105 

he was equal to the occasion — he was not going to be 
put off in that way. 

" Of course, the moon is not up," he replied ; "any 
one can see that, and that is the reason why I have 
come, for if the moon had been up, I could have seen 
it without your telescope at all ! " 

Although no explorer can ever reach our satellite, 
yet it is hardly an exaggeration to say that in some 
respects we know the geography of the moon a good 
deal better than we know the geography of the earth. 
Think of the continent of Africa. In that great country 
there are mighty tracts, there are vast lakes and ranges 
of mountains, of which we know but little. We could 
make a better map of Africa, so far at least as its broad 
outlines are concerned, if it were fastened up on our 
side of the moon than we actually possess at this 
moment. There is no spot on the nearer side of the 
moon as large as an ordinary parish in this country 
which has not been surveyed. There are maps and 
charts of the moon showing every part of it, which 
is as big as a good-sized field. Indeed, as there are 
no lunar clouds, the features of its surface are never 
obscured whenever our own atmosphere will permit 
us to make our observation. Artists have frequently 
sketched the lunar features, and there is plenty of 
material for them to work on. We have also had 
photographs taken of the moon, but there is a special 
difficulty to be encountered in taking photographs of 
celestial bodies which photographers of familiar objects 
on this earth do not experience. For a photograph to 
be successful, everybody knows that the first requisite 



106 STAR-LAND. 

is for the sitter to stay quiet while the plate is being 
exposed. This is, unhappily, just what the moon cannot 
do. We endeavor to obviate the difficulty by moving 
the telescope round so as to follow the moon in its 
progress. This can be done with considerable accuracy, 
but, unfortunately, there is another difficulty which 
lies entirely beyond our control. As the rays of light 
from the moon perform their journey through hundreds 
of miles of unsteady air, the rays are bent hither and 
thither, so that the picture is more affected by the 
atmosphere than in the case of a photographer's portrait 
taken in the studio. If we are merely viewing the 
moon through the telescope, the quivering effect on the 
rays of this long atmospheric voyage, though rather 
inconvenient, does not prevent us from seeing the 
object, and we can readily detect the true shape of 
each feature in spite of incessant fluctuations. When, 
however, these rays fall not on the eye, but on the 
photographic plate, they produce by their motion a 
picture which cannot be much magnified without be- 
coming very confused and wanting in sharpness. 
Nevertheless, for the general outlines of our satellite's 
appearance and for the portraiture of its splendid 
features we have derived the greatest assistance from 
photography. 

The adjoining picture (Fig. 40) gives a fair idea 
of what the full moon looks like when viewed through 
a small telescope. I do not, however, say that the 
lunar objects can then be observed under favorable 
conditions ; for when the moon is full is the very worst 
time for making observations of our satellite. In fact, 



WHEN TO STUDY THE MOON. 107 

at this phase you can hardly see anything except slight 
differences between the colors of different parts. The 
best time for observing the moon is at the first quarter ; 
but even then you can only observe satisfactorily those 



Fig. 40. — The Full Moon. 

objects which happen to lie along the border between 
light and shade. To study the moon properly you 
must, therefore, watch it during several different phases, 
from the time when it presents a thin and delicate 
crescent (just after new moon) until it has again waned 



108 STAR-LAND. 

to a thin and delicate crescent (just before the next 
new moon). We want the relief given by shadows to 
bring out the full beauty of lunar scenery. 

On the map you will first notice the large dark- 
colored patches which are so conspicuous on the 
moon's face. They are, apparently, the empty basins 
which great seas once filled. But if water was ever 
there it has at all events now quite disappeared. 
These dark parts are, no doubt, a good deal smoother 
than the rest of the surface ; but we can see many 
little irregularities which tell us that we are not look- 
ing at oceans. The chief features I want you to 
observe are the curious rings which you see in the 
figure ; there is a very well-marked one a little below 
the centre, and in the upper part many rings — large 
and small — are crowded together. We call them 
lunar craters. You will see what they are like from 
the model, of which a picture is shown in Fig. 42. 
But to realize from this picture the proper scale of 
the object, you should imagine it to be some miles 
in width. The cliffs which rise all round to form 
the wall, as well as the mountain which adorns the 
centre, are quite as high as any of the mountains in 
Great Britain. 

You may desire to know how we are able to measure 
the heights of mountains on the moon. That is what 
I am now going to show you ; and for this purpose we 
shall look at our imitation lunar crater. Here is the 
great ring, or circular enclosure, surrounded by cliffs, 
and here is a sharp mountain peak rising in the cen- 
tre. I shall ask to have the beam from the electric 



Vll'.W ON THE MOON. 



109 




I 







.■■;'.'■.' 













a 



Pig, u. — Vieiv on the Moon. 

s 
The tag« centra) crater is Hipparchus and above it is Albategnius. 



110 STAR-LAND. 

lamp turned on our model. You see how prettily 
it is lighted up. I have placed the lamp so that the 
beams are sloping; and I have done this with the 
express object of making the shadows long. In fact, 
as Ave look at a lunar crater, which lies on the border 
between light and shade, the sun illuminates the object 
under the same conditions as those shown in the figure. 
I dare say you have often noticed what long shadows 
are cast at sunset. Similar shadows are made to teach 



_ «* 




1IP5^1I1 life 


'"**' A 




Ih^^j^^Bs^^^^^^^ 




"■"*■ ^SfijHi^iP*^ 


^JM mS&0[^ ' 



Fig. 42. — Our Model of a Lunar Crater. 

the astronomer the altitudes of the lunar mountains ; 
for he measures the length of the shadow, and then by 
a little calculation he can find the height of the object 
by which that shadow has been cast. I shall suppose 
that Ave want to measure the height of a flagstaff 
(Fig. 43). It is quite possible to do this by merely 
measuring the length of the shadow which that flag- 
staff casts at noon. It would not be correct to say 
that the height of the flagstaff is the length of its 
shadow. This will, indeed, be the case if you are 
fortunate enough to make your measurement at or 



ON THE ORIGIN OF THE LUNAR CRATERS. Ill 

near London on either the 6th of April or the 5th 
of September. On all other days in the year a little 
calculation must be made, which I need not now men- 
tion, but which the astronomer, with the aid of his 
Nautical Almanac, can do in a very few minutes. In 
a similar manner, by measuring the lengths of the 




Fig. 43. — How we fotmd the Height of the Flagstaff. 

shadows on the moon, and by rinding the number of 
miles in the shadow, we are able to calculate the 
altitudes of the lunar mountains and of the ranges 
of cliffs by which the walled plains are surrounded. 



ON THE ORIGIN OF THE LUNAR CRATERS. 

We have now to offer an explanation of the curious 
rings which are the most characteristic features on 
the moon. To account for them Ave must look for a 
moment at some objects on the earth. You have all 



112 STAR-LAND. 

heard of volcanoes or burning mountains, such as 
Vesuvius or Etna, which occasionally break out into 
violent eruptions, and send forth great showers of ashes 
and torrents of molten lava. In the Sandwich Islands 
there is a celebrated volcano called Kilauea. It is like 
a vast lake of lava, so hot that it is actually molten, 
and glows with heat like red-hot iron. The adven- 
turous tourist who visits this crater can climb to the 
brink of a lofty range of cliffs which surround it, and 
gaze down upon the fervid sea beneath. Suppose that 
by some great change the internal heat which keeps 
this mighty basin glowing were to decline and go out, 
the sea of lava would cease to be liquid, and would 
ultimately grow hard and cold, and w^e should then 
have an immense flat plain, surrounded by a range of 
cliffs. Elsewhere in the Sandwich Islands examples 
of extinct craters may be found at the present day. 
Those who have studied these interesting localities 
point out how such terrestrial craters explain the 
ringed plains in the moon. It seems certain that in 
ancient days great volcanoes abounded on our satel- 
lite, and the rings were often much larger than those 
on the Sandwich Islands, some of them being one 
hundred miles or more in diameter. The volcanoes 
must long ago have been raging on the moon with a 
fury altogether unknown in any active volcanoes which 
this earth can now show. We can also surmise how 
the lofty mountain peak, which so often rises in the 
centre of a lunar ring, has been upheaved. When the 
fires had almost subsided, and the floor had grown 
nearly cold, one last and expiring effort is made by 



VOLCANOES ON THE MOON. 113 

which the congealing surface is burst through at the 
centre, and materials are shot forth which remain as 
the central mountain to the present day. 

I must, however, impress upon you that even our 
greatest telescopes never exhibit to us any volcanic 
eruptions at present going on in the moon ; in fact, it 
is most doubtful if any change has been noticed in the 
features on its surface since the date of the invention 
of the telescope. The volcanoes sculptured the crust 
of the moon into the form in which we see it, and that 
form our satellite has preserved for ages, of which we 
cannot estimate the duration. All the craters and all 
the volcanoes in the moon can only be described as 
extinct. 

It would be interesting for us to compare the present 
condition of the volcanoes in the earth with that of the 
ringed craters in the moon. The noisy volcanoes on 
our globe are those most talked about ; we often hear 
of Vesuvius being in eruption, and in August, 1883, 
there was a terrific eruption at Krakatoa, during which 
a large quantity of dust was shot up into the air, to 
such a height that it was borne right round the earth, 
and produced beautiful sunsets and unwonted sky hues 
in almost every country in the world. The explosion 
at Krakatoa made the loudest noise that history has 
recorded. Fortunately such convulsions of the earth do 
not often happen, for, on that occasion, the sea rushed in 
on the land, and thousands of lives were lost. There 
are said to be one hundred and fifty volcanoes on differ- 
ent parts of the earth, which are more or less active, but 
there are many others in which the fire has gone out, 



114 STAR-LAND. 

and which seem to be just as cold and just as extinct 
as any volcanoes in the moon. Even in our own islands 
there are abundant remains of ancient volcanoes. Masses 
of lava are found in many places where now there is no 
trace of an active volcano. Perhaps there is no more 
remarkable sight in the British Isles than that lofty 
rock which is crowned by Edinburgh Castle ; it is the 
remnant of a former volcano, while Arthur's Seat, close 
by, is another. In the centre of France is the beautiful 
district of Auvergne, in w T hich ancient volcanoes abound ; 
and the lava streams can be traced for miles across the 
country. These volcanoes have been extinct for thou- 
sands of years, during which time the lava has become 
largely covered with soil and vegetation, and in some 
places vineyards are cultivated upon it. 

We are now able to contrast the earth with the 
moon, in so far as volcanoes are concerned. On the 
earth we have some that are active, and a much 
greater number that are extinct. On the moon we 
find no active volcanoes, for there all are extinct. I 
can explain how this difference has arisen, but first let 
me show you a simple experiment. My assistant will 
kindly bring to me from that furnace two iron balls, 
which Ave placed there before the commencement of 
this lecture ; there they are, you see, both glowing with 
a bright red heat, for at present they are equally hot. 
We will place them on these stands, and allow them to 
grow cold. One of these balls is a small cannon-ball, 
four inches in diameter, while the other is only one inch. 
They are in the same proportion as the earth is to the 
moon; but look, even while I am speaking the balls 



INTERNAL HEAT. 115 

have ceased to preserve the same temperature, for the 
little one has become almost black from loss of its heat, 
while the large one still looks nearly as red as it did at 
the beginning; this simple experiment will illustrate 
the principle that two heated bodies will cool at very 
different rates, if their sizes be different, while the other 
conditions are the same. The small body will always 
cool faster than the large one. They need not be globes 
for this experiment ; if you put a poker and a knitting 
needle into the fire, and leave both there until they aie 
red-hot, and then put them out into the fender, you will 
speedily find that though they were at the same tem- 
perature when drawn from the fire, they do not long 
remain so ; indeed, the knitting needle has become cold 
enough to handle before the poker has ceased to glow. 
Our experiments have been made with, no doubt, small 
objects only, but the law about which they inform us 
will remain true, even for the greatest objects. 

Our earth at the present day shows many indications 
of being much hotter within than it is on the surface. 
The volcanoes themselves are mere outbreaks of incan- 
descent material from inside. Then there are - hot 
springs of water at Bath, which gush out from the 
earth. There are geysers of hot water in Iceland and 
in the Yellowstone Park in America, and in other 
places. And there are other indications also, with 
which every miner is familiar. Wherever a deep pit is 
sunk into the earth, the rocks below are always found 
to be warmer than those on the surface, and the deeper 
the pit the greater is the heat that is encountered. 
Thus, from all over the world we obtain proofs of the 



116 STAR-LAND. 

present existence of internal heat. Great as is the 
earth, we must still apply the simple common-sense 
principles that we use in our everyday life here. Let 
me give an illustration. Suppose that a servant came 
into the room and placed a jug of water on the table, 
and that an hour afterwards you went to the jug of 
water and found it to be cold, you would not from that 
fact alone be able to infer anything with certainty, as 
to whether the water had been warm or cold when it 
was brought in. It might have been perfectly cold, as it 
is at present, though on the other hand the water might 
have been warm at first, and have since cooled down to 
the temperature of the room during the hour. 

Suppose, however, that when you went to the jug of 
water, which had stood on the table for an hour, you 
found it tepid, no matter how slightly its tenrperature 
might be above that of the room, do you not see the 
inference you would be able to draw? You would 
argue in this way: that water has still some heat; it 
must, of course, be gradually cooling, and therefore it 
was hotter a minute ago than it is now ; it was hotter 
still two minutes ago, or ten minutes ; and must have 
been very hot and perhaps boiling when it was brought 
in an hour ago. 

I want you to apply exactly the same reasoning to 
our earth. It is, as I have shown you, still hot and 
warm inside. Of course, that heat is gradually becom- 
ing lost ; so that the earth will from year to year grad- 
ually cool down, though at an extremely slow rate. 
But we must look back into what has happened during 
past ages. Just as we inferred that the jug must have 



A HOT MOON. 117 

contained very hot water an hour before from the mere 
fact that the water was still warm, so we are entitled to 
infer, from the fact that the earth still retains some 
heat, that it must in ages gone by have been exceed- 
ingly hot. In fact, the further we look back, the hotter 
do we see the earth growing, until at last we are con- 
strained to think of a period, in the excessively remote 
past, long ere life began to dawn on this earth, when 
even the surface of the earth was hot. Back further 
still we see the earth no longer covered with the hard, 
the dark, and the cold surface we now find ; we are to 
think of it in these primitive times as a huge glowing 
mass, in which all the substances that now form the 
rocks were then incandescent, and even molten material. 
There is good reason for knowing that in those early 
times the moon also was molten with heat; and thus 
our reasoning has led us to think of a period when 
there were two great red-hot globes — one of which 
had about four times the diameter of the other — start- 
ing on their career of gradually cooling down. Recall 
our little experiment with the two cooling globes of 
iron; imagine these globes to preserve their relative 
proportions, but that one of them was 8000 miles and 
the other 2000 miles across. Ages will, no doubt, 
elapse ere they part with their heat sufficiently to allow 
the surfaces to cool and to consolidate. We may, how- 
ever, be sure that the small globe will cool the faster, 
that its outside will become hard sooner than will the 
surface of the large one, and long after the small globe 
has become cold to the centre, the large one may con- 
tinue to retain some of its primeval heat. We can thus 



118 STAR-LAND. 

readily understand why all the volcanoes on the moon 
have ceased — their day is over. It is over because the 
moon, being so small, has grown so cold that it no 
longer sustains the internal fires which are necessary 
for volcanic outbreaks. Our earth, in consequence of 
its much greater size, has grown cold more slowly. It 
has no doubt lost the high temperature on the exterior, 
and its volcanic energy has probably abated from what 
it once was. But there is still sufficient power in the 
subterranean fires to awaken us occasionally by a Kra- 
katoa, or to supply Vesuvius with sufficient materials 
and vigor for its more frequent outbursts. The argu- 
ment shows us that the time will at last come when this 
earth shall have parted with so large a proportion of its 
heat that it will be no longer able to provide volcanic 
phenomena, and then we shall pass into the exhausted 
stage which the moon attained ages ago. 

THE MOVEMENTS OF THE MOON. 

Though the moon is going round and round the 
earth incessantly, yet it always manages to avoid afford- 
ing us a view of what is on the other side. Our satel- 
lite always directs the same face towards the earth, and 
we may reasonably conjecture that the other side is 
covered, like the side we know, with rings and other 
traces of former volcanoes. In this respect the moon 
is quite a peculiar object. The other great celestial 
bodies, such as the sun or Jupiter, turn round on their 
axes, and show us now one side and then the other, 
with complete impartiality. The way in w^hich the 



HOW THINGS FALL. 119 

moon revolves may be illustrated by taking your watch 
and chain, and as you hold the chain at the centre mak- 
ing the watch revolve in a circular path. At every 
point of its path the ring of the watch is, of course, 
pointed to the centre where the chain is held. If you 
imagine your eye placed at the centre, to represent the 
earth, the movements of the watch would exemplify the 
way the moon turns round it. 

One more point I must explain about the moon before 
we close this lecture. There is nothing more familiar 
than the fact that a heavy body will fall to the ground. 
Indeed, it hardly matters what the material of the body 
may be, for you see I have a small iron ball in one hand 
and I hold a cork in the other. I drop them at the 
same moment, and they reach the ground together. 
Perhaps you would have expected that the cork would 
have lagged behind the iron. I try the experiment 
again and again, and you can see no difference in the 
times of their falling, though I do not say this would be 
true if they were dropped from the top of the Monument. 
In general we may say that bodies let drop will fall six- 
teen feet in the first second. Even a bit of paper and 
a penny piece will fall through the same height in 
the same time if you can get over the difficulty of the 
resistance of the air. This is easily managed. Cut a 
small piece of tissue paper which will lie flat on the top 
of the penny, and hold the penny horizontal with the 
paper uppermost. Though there is nothing to fasten 
the paper to the penny, you will find that they fall 
together. If we could conduct the experiment of drop- 
ping the penny and the bit of paper in a vacuum, then, 



120 STAR-LAND. 

whether the paper was laid on the penny or placed in 
any other way, the two objects would reach the table at 
the same moment if released at the same moment at equal 
heights. 

Wherever we go we find that bodies will always 
tend to fall in towards the centre of the earth ; thus in 
New Zealand, at the opposite side of our globe from 
where we are now standing, bodies will fall up towards 
us, and this law of falling is obeyed at the top of a 
mountain as it is down here. No matter how high 
may be the ascent made in a balloon, a body released 
will fall towards the earth's centre. Of course, we can 
only ascend some five or six miles high, even in the 
most buoyant of balloons ; but we know that the attrac- 
tion by which bodies are pulled downwards towards the 
earth extends far beyond this limit. If we could go 
ten, twenty, or fifty miles up, we should still find that 
the earth tried to pull us down. Nor, even if you could 
imagine an ascent made to the height of 1000 miles, 
would gravitation have ceased. A cork or an iron ball, 
or any other object dropped from the height of 1000 
miles, would assuredly tumble down on the ground 
below. 

Suppose that by some device we were able to soar 
aloft to a height of 4000 miles. I name that elevation 
because we should then be as high above the earth as 
the centre of the earth is below our feet. We should 
have doubled our distance from the centre of the earth, 
and the intensity of the gravitation would have decreased 
to one-quarter of what it is at the surface. A body 
which at the earth's surface falls sixteen feet in a second 



A WONDERFUL CANNON. 121 

would there fall only four feet in a second, and the 
apparent weight of any body would be so much reduced 
that it would seem to weigh only a quarter of what it 
weighs down here. Thus, the higher and higher we 
go, the less and less does gravity become ; but it does 
not cease, even at a distance of millions of miles. 
Therefore you might say that as gravity tries to pull 
everything down, wherever it may be, why does it not 
pull down the moon ? This is a difficulty which we 
must carefully consider. Supposing that the earth and 
the moon were simply held apart, both being at rest, 
and that then the moon were to be let go, it would no 
doubt drop down directly on the earth. The movement 
of the moon would, however, be very different if, instead 
of being merely let fall, it was thrown sideways. The 
effect of the earth's pull upon the moon would then be 
shown in keeping the moon revolving around us instead 
of allowing it to fly away altogether, as it would have 
done had the earth not been there to attract it. 

We can explain this by an illustration. On the top 
of a mountain I have placed a big cannon (Fig. 44). 
We fire off the cannon, and the bullet flies away in a 
curved path, with a gradual descent until it falls to the 
ground. I have made the mountain look hundreds of 
times larger than any mountain could possibly be ; and 
now I want you to imagine a cannon far stronger and 
gunpowder more potent than any powder or cannon 
that has ever yet been manufactured. Fire off a bullet 
with a still greater charge than the last time, and now 
the path is a much longer one, but still the bullet curves 
down so as ultimately to fall on the earth. But make 



122 STAR-LAND. 

now one final shot with a charge sufficiently powerful, 
and away flies the bullet, following this time the curva- 
ture of the earth, for the earth's attraction has the effect 
of bending the path of the bullet from a straight line 




Fig. 44. — An Illustration to explain the Movement of the Moon. 

into this circular form. By the time the bullet has 
travelled a quarter of the w^ay round, it is no nearer to 
the earth than it was at first, nor has it parted with any 
of its original speed. Thus, notwithstanding its long 
journey, the bullet has practically just as much energy 
as when it first left the muzzle of the cannon. Away 
it will fly round another quarter of the earth, and still 



IS THERE LIFE ON THE MOON? 123 

in the same condition it will accomplish the third and 
the fourth quarters, thus returning to the point from 
which it started. If we have cleared the cannon out of 
the way, the bullet will fly again over the mountain 
top without having lost any of its speed by its voyage 
round the earth. Therefore it will be hi a condition to 
start again, and thus to revolve around the earth per- 
manently. If, then, from the top of a mountain 240,000 
miles high a great bullet 2000 miles in diameter had 
once been projected with the proper velocity, that bul- 
let would continue forever to circle round and round 
the earth, and even though the mountain and the 
cannon disappeared, the motion would be preserved 
indefinitely. This illustration will, at all events, show 
how a continuous revolution of the moon round the 
earth can exist, notwithstanding that the earth is con- 
stantly pulling our satellite down towards its surface. 

ON THE POSSIBILITY OF LIFE IN THE MOON. 

Astronomers are often asked whether any animals 
can be living on the moon. No observations we can 
make with the telescope can answer that question 
directly. There are great plains to be seen on the 
moon, of course, but even if there were elephants tramp- 
ing over those plains, our telescopes could not show 
them. Nor will our instruments pronounce at once 
whether plants or trees flourish on the moon. The 
mammoth trees of California are so big that a tunnel 
has been cut through the trunk of one large enough to 
give passage for a carriage and pair. Even if there 



124 STAR-LAND. 

were trees as big as this on the moon, they would not 
be visible from the most famous observatories. 

Let us think what we should ourselves experience if 
we could in some marvellous manner be transferred 
from the earth to its satellite, and tried to explore that 
new and wonderful country. Alas, we should find it 
utterly impossible to live there for an hour, or even for 
a minute ! Troops of difficulties would immediately 
beset us. The very first would be the want of air. 
Ponder for a moment on the invariable presence of air 
around our own globe. Even if you climb to the top 
of a high mountain, or if you take a lofty voyage in a 
balloon, you are all the time bathed in air. It is air 
which supports the balloon, just as a cork is buoyed up 
by water. In all circumstances, we must have air to 
breathe. In that air is oxygen gas, and we must have 
oxygen incessantly supplied to our lungs to reinvigorate 
our blood. We require, too, that this oxygen shall be 
diluted with a much larger amount of nitrogen gas, for 
our lungs and system of circulation are adapted for 
abode in that particular mixture of gases which we find 
here. The atmosphere becomes more and more rarefied 
the higher we ascend, and apparently terminates alto- 
gether some two or three hundred miles over our heads. 
Beyond the limits of the atmosphere it seems as if empty 
space would be met with all the way from the earth to 
the moon. We could not procure a single breath of 
air, and life would be, of course, impossible. Even at 
a height of three or four miles, respiration becomes 
difficult, and doubtless life could not possibly be sus- 
tained at a height of ten miles. 



NO AIR ON THE MOON. 125 

It is therefore plain that for a voyage to the moon 
we should require an ample supply of air, or, at least, 
of life-giving oxygen, which in some way or other was 
to be inhaled during the progress of the journey. When 
at length 240,000 miles had been traversed, and we 
were about to land on the moon, we would first of all 
ascertain whether it was surrounded with a coating of 
air. Most of the globes through space are, so far as 
we can learn, covered and warmed with an enveloping 
atmosphere of some kind ; but, unhappily, the poor 
moon has been left entirely, or almost entirely, without 
any such clothing. She is quite bare of atmosphere at 
all comparable in density or in volume to that which 
surrounds us, though possibly we do now and then per- 
ceive some traces of air, or of some kind of gas, in small 
quantities in the lunar valleys. 

I am sure each intelligent boy or girl will want to 
know how we are able to tell all this. We have never 
been at the moon, and how then can we say that it is 
nearly destitute of air? Nor can our telescope answer 
this question immediately, for you could hardly expect 
to see air, even if it were there. How then are we able 
to make such assertions ? There are many different 
ways in which we have learned the absence of air from 
the moon. I will tell you one of the easiest and the 
most certain of these methods. First let me say that 
air is not perfectly transparent. No doubt I can see 
you, and you can see me, though a good many feet of 
air may lie between us ; but when we deal with dis- 
tances much greater, there is a very simple way in which 
we can show that air is not quite transparent. In the 



126 STAR-LAND. 

evening, when the sun is setting and the sky is clear, 
you can look at him without discomfort ; but in the 
middle of the day you know that it is impossible to look 
at the sun without shading your eyes with smoked glass 
or protecting them by some similar contrivance. The 
reason is, that when the sun is either setting or rising 
we look at it through an immense thickness of air, 
which not being perfectly transparent stops some of the 
light. Thus it is that the sun in these circumstances 
loses its dazzling brilliancy, and we can view it without 
discomfort. 

At the seaside you can notice the same effect in a 
different manner. Go out on a fine and clear night, 
when the stars in their thousands are glittering over- 
head, and then look down gradually towards the horizon, 
and you will find the stars becoming fainter and 
fainter. Indeed, even the brightest star cannot be 
seen when it is at the horizon, because an immense 
thickness of the atmosphere is not transparent. 

We can now state the argument by which we may 
prove that there is little or no air on our satellite. 
The moon will frequently pass between the earth and a 
star, and when the star is a really bright one the obser- 
vations that can be made are of great interest. Let me 
first describe what we actually see. The star is shining 
brightly until the moment when the moon eclipses it. 
Generally speaking, its disappearance is instantaneous. 
But this would not be the case if the moon were encir- 
cled with an atmosphere. If the moon were coated 
with air, the light from the star would not be extin- 
guished instantly ; it would gradually decline, accord- 



NO WATER ON THE MOON. 127 

ing as it had to pass through more and more of the 
moon's atmosphere. Thus you would find that the star 
dwindled down in brightness before the solid body of 
the moon had advanced far enough to shut it out. The 
sudden extinction of the stars demonstrates the airless 
state of our satellite. 

There would be another insuperable difficulty in 
adopting the moon as a residence, even supposing that 
you could get there. Water is absent from its surface. 
We have examined every part of it, and we find no evi- 
dences of seas or of oceans, of lakes or rivers ; we never 
see anything like clouds or mists, which are, of course, 
only water in the vaporous form. We are, therefore, 
assured that, so far as water is concerned, the moon is 
an absolute desert. This is, perhaps, the most striking 
contrast between the aspect of the earth and the aspect 
of the moon. Were an astronomer on the moon to look 
at our earth he would find most of its surface concealed 
beneath clouds, and through the openings in these 
clouds he would see that by far the greater part of this 
globe was covered by the expanse of ocean ; in fact, 
when the lunar astronomer had realized the prevalence 
of water upon this earth, either in the form of ocean or 
cloud, I feel sure he would come to the conclusion that 
nothing could live here except seals or other amphibious 
animals. 

Owing to the absence of air and water, the moon 
would be totally disqualified for the support of life of 
those types in which we know it. For air and water are 
necessary to every animal, from the humblest animal- 
cule up to whales or elephants. Air and water are 



128 STAR-LAND. 

necessary for every form of vegetable life, from the 
lichen which grows on a stone up to the noble old oak 
of the forest. But even supposing that we could land 
on the moon, bearing with us an ample supply of 
oxygen to breathe, and of water to drink, we should 
find ourselves perplexed and embarrassed, to say the 
very least of it, by an extraordinary difference that 
would immediately attract our notice. That familiar 
experience of gravity, or the weights of things, which 
we have acquired in our residence on a great globe like 
the earth, would seem ludicrously altered when we 
began to walk about on a little globe like the moon. 
We should be astonished at the transformation by 
which the weight of everything was much lessened ; 
when you pulled out your watch you would hardly feel 
it at the end of the chain ; it would seem like a mere 
shell ; but yet the watch is all right, it is going as well 
as ever. Nothing has altered about it except its weight. 
A big stone attracts your notice, and, to your amaze- 
ment, you find that it does not weigh so much as a 
piece of wood of the same size would weigh down here. 
A stone that you could hardly stir on the earth, you 
can carry about on the moon. Nor is this to be ex- 
plained by any peculiarity in the constitution of the 
lunar stone. Most probably it will be not very dissimi- 
lar to some of the rocks on the earth. The relative 
lightness of a lunar stone is not due to its being formed 
of some very special material ; we must seek for some 
other explanation. Every object on the moon would 
be found only one-sixth as heavy as the same object on 
the earth. A sturdy laborer at one of the docks can 



HOW THINGS WOULD WEIGH. 



129 



carry one sack of corn on his back here, and he finds 
that this load is as much as is convenient. He would, 
however, discover, were he placed on the moon, that his 
load had suddenly become lightened to one-sixth part 
(Fig. 45). The laborer would find that he could carry 
six sacks of corn on the moon without making a greater 



A. 



# 






Fig. 45. — The Lessened Gravitation on the Moon. 

effort than the support of a single sack on the earth 
cost him. To explain how such a change as this has 
occurred, look at these two pictures : one shows the 
laborer on a small body like the moon, the other shows 
him on a great globe like the earth. What the laborer 
actually does feel is not quite so simple a thing as he 
imagines. He imagines that it is the weight of the 
corn, and the corn alone, which produces that pressure 
on his shoulders which he knows so well. But that is 
not exactly the manner in which the philosopher will 
look at the same question. What the laborer does 
actually feel is the attraction between the earth beneath 



130 STAR-LAND. 

his feet and the corn on his back. It is this force 
which produces the pressure on his shoulders. Its 
magnitude no doubt depends upon the quantity of corn 
in the sack, but it also depends on the quantity of mat- 
ter on the earth beneath his feet. In fact, the force 
between two attracting bodies depends upon the masses 
of both the attracting bodies. When the laborer is 
transferred to the moon, of which the mass is so much 
less than that of the earth, the attraction is less there 
than it is here, even though the corn is the same in the 
two cases. 

Many odd instances could be given of the extraordi- 
nary consequences of life on a world where all weights 
are reduced to a sixth part. One occurred to me the 
other day when I saw a postman going his rounds with 
an amazing load of Christmas presents and parcels. I 
thought, how much happier must be the lot of a post- 
man on the moon, if such functionaries are wanted 
there ! All the presents of toys or more substantial 
donations might be the same as before, the only altera- 
tion would be that they would not feel nearly so heavy. 
A box which contains a pound of chocolate bonbons 
might still contain exactly the same quantity of sweet- 
meat on the moon, but the exertion of carrying it 
would be reduced to one-sixth. It would only weigh 
as much as two or three ounces do on the earth. Our 
streets provide another admirable illustration of the 
drawbacks of our life here as compared with the facili- 
ties offered by life on the moon. I feel quite confident 
that no perambulators can be necessary there. I cannot 
indeed say that there are babies to be found on the 



LIGHTNESS OF BODIES ON THE MOON. 131 

moon, but of this I am certain, that even if the lunar 
babies were as plump and as sturdy as ours, they must 
still only weigh about a sixth as much as ours do. A 
lunar nurse would scorn to use a perambulator, even 
for a pair of twins ; she might take them both out on 
her arm for an airing, and even then only bear one-third 
of the load that her terrestrial sister must sustain if she 
is carrying but a single child. 

The lightness of bodies in the moon would entirely 
transform many of our most familiar games. In 
cricket, for instance, I don't think the bowling would 
be so much affected, but the hits on the moon would be 
truly terrific. I believe an exceptionally good throw of 
the cricket-ball here is about a hundred yards, but the 
same man, using the same ball and applying the same 
force to it, would send the ball six hundred yards on 
the moon. So, too, every hit would in the lunar game 
carry the ball to six times the distance it does here. 
Football would show a striking development in lunar 
play ; a good kick would not only send the ball over 
the cross-bar, but it would go soaring over the houses, 
and perhaps drop in the next parish. 

Our own bodies would, of course, participate in the 
general buoyancy, so that, while muscular power re- 
mained unabated, we should be almost able to run and 
jump as if we had on the famous seven-league boots. 
I have seen an athlete in a circus jump over ten horses 
placed side by side. The same athlete, making the 
same effort, would jump over sixty horses on the moon. 

A run with a pack of lunar foxhounds would indeed 
be a marvellous spectacle. There need be no looking 



132 STAR-LAND. 

round by timid horsemen to find open roads or easy 
gaps. The five-barred gate itself would be utterly 
despised by a huntsman who could easily clear a hay- 
rick. It would hardly be worth taking a serious jump 
to clear a canal unless there was a road and a railway 
or so, which could be disposed of at the same time. 

To illustrate this subject of gravitation in another 
way, suppose that we were to be transferred from this 
earth to some globe much greater than the earth — to 
a globe, for instance, as large and massive as the sun. 
We can then show that the weight of every object 
would be increased. Indeed, everything would weigh 
about twenty-seven times as much as we find it does 
here. To pull out your watch would be to hoist a 
weight of about five or six pounds out of your pocket. 
Indeed, I do not see how you could draw out your 
watch, for even to raise your arm would be impossible ; 
it would feel heavier by far than if it were made of 
solid lead. It is, perhaps, conceivable that you might 
stand upright for a moment, particularly if you had a 
wall to lean up against ; but of this I feel certain, that 
if you once got down on the ground, it would be utterly 
out of your power to rise again. 

These illustrations will at least answer one purpose : 
they will show how difficult it is for us to form any 
opinion as to the presence or the absence of life on the 
other globes in space. We are just adapted in every 
way for a residence on this particular earth of a partic- 
ular size and climate, and with atmosphere of a par- 
ticular composition. Within certain slender limits our 
vital powers can become accommodated to change, but 



ANIMAL AND VEGETABLE LIFE. 133 

the conditions of other worlds seem to be so utterly 
different from those we find here, that it would probably 
be quite impossible for beings constituted as we are 
to remain alive for five minutes on any other globe 
in space. 

It is, however, quite another question as to whether 
there may not be inhabitants of some kind on many of 
4-he other splendid globes. We have through the wide 
extent of space inconceivable myriads of worlds, pre- 
senting, no doubt, every variety of size and climate, of 
atmosphere and soil. It seems quite preposterous to 
imagine that among all these globes ours alone should 
be the abode of life. The most reasonable conclusion 
for us to come to is that these bodies may be endowed 
with life of types which are just as appropriate to the 
physical conditions around them as is the life, both 
animal and vegetable, on this globe to the special cir- 
cumstances in which it is placed. 



LECTURE III. 

THE INNER PLANETS. 

Mercury, Venus, and Mars — How to make a Drawing of our System — 
The Planet Mercury — The Planet Venus — The Transit of Venus — 
Venus as a World — The Planet Mars and his Movements — The 
Ellipse — The Discoveries made by Tycho and Kepler — The Discov- 
eries made by Newton — The Geography of Mars — The Satellites of 
Mars — How the Telescope aids in Viewing Faint Objects — The 
Asteroids, or Small Planets. 

MERCURY, VENUS, AND MARS. 

We can hardly think of either the sun or the moon 
as a world in the sense in which our earth is a world, 
but there are some bodies called planets which seem 
more like worlds, and it is about them that Ave are now 
going to talk. Besides our Earth there are seven 
planets of considerable size, and a whole host of insig- 
nificant little ones. These planets are like ours in a 
good many respects. One of them, Venus, is about 
the same size as this earth ; but the two others, Mercury 
and Mars, are very much smaller. There are also some 
planets very much larger than any of these, namely, 
Jupiter, Saturn, Uranus, and Neptune. We shall in 
this lecture chiefly discuss three bodies, namely, Mer- 
cury, Venus, and Mars, which, with the earth, form 
the group of " inner " planets. 

The planets are all members of the great family 
dependent on the sun. Venus and the earth may be 
considered the pair of twins, alike in size and weight. 

134 



MOVING CELESTIAL BODIES. 135 

Mercury and Mars are the babies of the system. The 
big brothers are Jupiter and Saturn. All the planets 
revolve round the sun, and derive their light and their 
heat from his beams. We should like to get a little 
closer to some of our fellow-planets and learn their 
actual geography. Unfortunately, even under the most 
favorable circumstances, they are a very long way off. 
They are many millions of miles distant, and are always 
at least a hundred times as far as the moon. But far 
as the planets may be, astronomers have been familiar 
with their existence for ages past. I can give you a 
curious proof of this. You remember how we said the 
first and the second days of the week were called after 
the sun and the moon, Sun-day and Moon-day, or Mon- 
day, respectively. Let us see about the other days. 
Tuesday is not quite so obvious, but translate it into 
French and Ave have at once Mardi ; this word means 
nothing but Mars' day, and our Tuesday means exactly 
the same. Wednesday is also readily interpreted by 
the French word Mercredi, or Mercury's day, while 
Venus corresponds to Friday. Jupiter's day is Thurs- 
day, while Saturn's day is naturally Saturday. The 
familiar names of the days of the week are thus asso- 
ciated with the seven moving celestial bodies which 
have been known for uncounted ages. 

HOW TO MAKE A DRAWING OF OUR SYSTEM. 

I want every one who reads this book to make a little 
drawing of the sun and the planets. The apparatus 
that you will need is a pair of compasses ; any sort of 



136 



STAR-LAND. 



compasses that will carry a bit of pencil will do. You 
must also get a little scale that has inches and parts of 
inches divided upon it ; any carpenter's rule will answer. 
The drawing is intended to give a notion of the true 
sizes and positions of the fine family of which the earth 
is one member. The figure I have given (Fig. 46) is not 
on so large a scale as that which I ask you to use, and 



Mars 



/Venus*/ Mercury 



Bun / 



sCxEarth 
\ 



1 i 





\ 


\ 88daY s 
22*5 days 


\ 




365~days 




X x 


687 d'ays 


Fig. 


46.- 


-The Orbits of the Four Inner Planets. 



which I shall here mention. Try and do the work neatly, 
and then pin up your little drawings where you will be 
able to see them every day until you are quite familiar 
with the notion of what we mean by our solar system. 



MAKING A MAP. 137 

First open the compasses one inch, and then describe 
a circle, and mark a dot on this as " Mercury," in neat 
letters, and also write on the circle " 88 days." At the 
centre you are to show the " Sun." This circle gives 
the track followed by Mercury in its journey round the 
sun in the period of 88 days. Next open your com- 
passes to If in., which you must do accurately by the 
scale. The circle drawn with this radius shows the 
relative size of the path of Venus, and to indicate 
the periodic time, you should mark it, " 225 days." The 
next circle you have to draw is a very interesting one. 
The compass is to be opened 2i in. this time, and the 
path that it makes is to be marked " 365 days." This 
shows the high road along which we ourselves journey 
every year, along which we are, indeed, journeying at 
this moment. If you wanted to obtain from your figure 
any notions of the true dimensions of the system, the 
path of the earth will be the most convenient means of 
doing so. The earth is 93,000,000 miles from the sun, 
and our drawing shows its orbit as a circle of 2| in. 
radius. It follows that each inch on our little scale 
will correspond to about 37,000,000 miles. As, there- 
fore, the radius of the orbit of Mercury has been taken 
to be one inch, it follows that the distance of Mercury 
from the sun is about 37,000,000 miles. 

We have, however, still one more circle to draw 
before we complete this little sketch. The compass 
must now open to four inches, and a circle which 
represents the orbit of Mars is then to be drawn. We 
mark on this " 687 days," and the inner part of the 
solar system is then fully represented. You see, this 



138 STAR-LAND. 

diagram shows how our earth is in every sense a planet. 
It happens that one of the four planets revolves out- 
side the earth's path, while there are two inside. By 
marking the days on the circles which show the periods 
of the planets, you perceive that the further a planet 
is from the sun, the longer is the time that it takes to 
go round. Perhaps you will not be surprised at this, 
for the length of the journey is, of course, greater in 
the greater orbits; but this consideration will not 
entirely explain the augmentation of the time of revolu- 
tion. The further a planet is from the sun, the more 
slowly does it actually move, and therefore, for a double 
reason, the larger orbit will take a longer time. From 
London to Brighton is a much longer journey than from 
London to Greenwich, and, therefore, the journey by 
rail to Brighton will, of course, be a longer one than 
by rail to Greenwich. But suppose that you compared 
the railway journey to Greenwich with the journey, 
not by rail, but by coach, to Brighton, here the com- 
parative slowness of the coach would form another 
reason besides the greater length of the journey for 
making the Brighton trip a much more tedious one than 
that to Greenwich. Mars may be likened to the coach 
which has to go all the way to Brighton, while Mercury 
may be likened to the train which flies along over the 
very short journey to Greenwich. 

We can easily show from our little sketch that 
Mercury must be moving more quickly than Mars, for 
the radii of the two circles are respectively one inch 
and four inches, and therefore the path of Mars must 
be four times as long as the orbit of Mercury. If 



THE SIZES OF THE PLANETS. 



139 



MARS 

• ; 


M ^UPITE? 


^^ THE EARTH 


^Hj gSM 


(The Ruddy Planet) 


MERCURY i 






(The Planet M 
nearest the ^M 






Sun) ■ 


The greatest 
Planet 




m 


d 


^T^Jrr^^ 


wM Herschel's ^M 
H Planet 




The Planet 
With the Rings 


^m The farthest ^M 
Planet 



Fig. 47.— Comparative Sizes of the Planets. 



Mars moved as fast as Mercury, he would, of course, 
require only four times as many days to complete his 
large path as Mercury takes for his small path; but 
four times 88 is 352, and, consequently, Mars ought to 



140 



STAR-LAND. 



get round in 352 clays if he moved as fast as Mercury 
does. As a matter of fact, Mars requires nearly twice 

that number of days ; 
indeed, no less than 
687, and hence we 
infer that the aver- 
age speed of Mars 
cannot be much 
more than half that 
of Mercury. 

To appreciate 
duly the position of 
the earth with re- 
gard to its brothers 
and sisters in the 
sun's family it will 
be necessary to use 
your compasses in 
drawing another 
little sketch, by 
which the sizes of 
the four bodies 
themselves shall be 
fairly represented. 
Remember that the 
last drawing showed 
nothing whatever about the sizes of the bodies ; it merely 
exhibited the dimensions of the paths in which they 
moved. As Mercury is the smallest globe of the four, we 
shall open the compasses half an inch and describe a 
circle to represent it. The earth and Venus are so nearly 




THE PLANET MERCURY. 141 

the same size (though the earth is a trifle the larger) 
that it is not necessary to attempt to exhibit the 
difference between them, so we shall represent both 
bodies by circles, each 1 j inches in radius. Mars, like 
Mercury, is one o( the globes smaller than the earth, 
and the circle that represents it will have a radius of 
| of an inch. You should draw these figures neatly, 
and by a little shading make them look like globes. 
It would be better still if you were to make actual 
models, taking care, of course, to give each of them 
the exaet size, A comparative view of the principal 
planets is shown in Fig. 47. 

THE PLANET MERCURY, 

Quicksilver is a bright and pretty metal, and, unlike 
every other metal, it is a liquid under ordinary circum- 
stances. If you spill quicksilver, it is a difficult task to 
gather the liquid up again. It breaks into little drops, 
and you cannot easily lift them with your lingers: they 
slip away and escape your grasp. Quicksilver will run 
easily through a hole so small that water would hardly 
pass, and it is so heavy that an iron nail or a bunch 
of keys will float upon it. Now, this heavy, bright, 
nimble metal is known by another name besides quick- 
silver; a chemist would eall it mercury, and the astron- 
omers use exactly the same word to denote a pretty, 
bright, nimble, and heavy planet which seems to try to 
elude our vision. Though Mercury is so hard to see, 
vet it was discovered so long ago, that all record is lost 
of who the discoverer was. 



142 STAR-LAND. 

You must take special pains if you want to see 
the planet Mercury, for during the greater part of 
the year it is not to be seen at all. Every now and 
then a glimpse is to be had, but you must be on the 
alert to look out just after sunset, or you must be up 
very early in the morning so as to see it just before 
sunrise. Mercury is always found to bo in attendance 
on the sun, so that you must search for him near the 
sun ; that is, low down in the west in the evenings, or 
low down in the east in the mornings. To ascertain 
the proper time of the year at which to look for him 
you must refer to the almanac. 

We have seen how Mercury revolves in a path inside 
that of Venus, and it is therefore nearer to the sun. 
Indeed, Mercury is so close to the sun that it is 
generally overpowered by his brilliance and cannot be 
seen at all. Like every other planet, Mercury is 
lighted by the sun's rays, and shows phases in the 
telescope just as the moon does (Fig. 48). In this 
figure the different apparent sizes of the planet at 
different parts of its patli are shown. Of course the 
nearer Mercury is to the earth the larger does it 
seem. 

If we can only see Mercury so rarely, and if even 
then it is a very long way off, does it not seem strange 
that we can tell how heavy it is ? Even if we had a 
pair of scales big enough to hold a planet, what, it 
may be asked, would be the use of the scales when 
the body to be weighed was about a hundred millions 
of miles away? Of course the weighing of a planet 
must be conducted in some manner totally different 



WEIGHING THE PLANET MERCURY. 143 

from the kind of weighing that we ordinarily use. 
Astronomers have, however, various methods for weiffh- 
ing these big globes, even though they can never touch 
them. We do not, of course, want to know how man)' 
pounds, or how many millions of tons they contain : 
there is but little use in trying to express the weight 
in that way. It gives no conception of a planet's 
true importance. One world must be compared with 
another world, and we therefore estimate the weights 
of the other worlds by comparing them with that of 
our own. AVe accordingly have to consider Mercury 
placed beside the earth, and to see which of the two 
bodies is the bigger and the heavier, or what is the 
proportion between them. It so happens that Mercury, 
viewed as a world, is a very small body. It is a good 
deal less in size than our earth, and it is not nearly 
so massive. To show you how we found out the 
mass of Mercury I shall venture on a little story. It 
will explain one of the strange devices that astronomers 
have to use when they want to weigh a distant body 
in space. 

There was once, and there is still, a little comet 
which flits about the sky ; we shall call it after the 
name of its discoverer, Encke. There are sometimes 
splendid comets which everybody can see — we will 
talk about these afterwards — but Encke is not such 
a one. It is very faint and delicate, but astronomers 
are interested in it, and they always look out for it 
with their telescopes ; indeed, they could not see the 
poor little thing without them. Encke goes for long 
journeys through space — so far that it becomes quite 



144 STAR LAM). 

invisible, and remains out of sight for two or three 
years. All this time it is tearing along at a tremendous 
speed. If you were to take a ride on the comet, it 
would whirl you along Ear more swiftly than if you 
were sitting on a cannon-hall. When the comet has 
reached the end of its journey, then it turns round and 
returns by a different road, until at last it comes near 
enough to show itself. Astronomers give it all the 
welcome they can, but it won't remain; sometimes it 
will hardly stay long enough for us to observe that it 
has come at all, and sometimes it is so thin and worn 
after all its wanderings that we are hardly able to see 
it. The comet never takes any rest ; even during its 
brief visit to us it is scampering along all the time, and 
then again it darts off, gradually to sink into the depths 
of space, whither even our best telescopes cannot follow 
it. No more is there to be seen of Encke for another 
three years, when again it will come back for a while. 
Encke is like the cuckoo, which only comes for a brief 
visit every spring, and even then is often not heard by 

many who dearly Love his welcome note; but. Encke is 

a greater stranger than the cuckoo, for the comet never 
repeats his visit of a few weeks more than once 4 in three 
years; and he is then so shy that usually very lew 
catch a glimpse of him. 

An astronomer and a mathematician were great 
friends, and they used to help each other in their 
work. The astronomer watched Encke's comet, noted 

exactly where it was, on each night it was visible, and 
then told the mathematician all lie had seen. Provided 
with this information the mathematician sharpens his 



THE ASTRONOMER AND THE COMET. 145 

pencil, sits down at his desk, and begins to work long 
columns of figures, until at length he discovers how 
to make a time table which shall set forth the wander- 
ings of Encke. He is able to verify the accuracy of 
his table in a very unmistakable way by venturing 
upon prophecies. The mathematician predicts to the 
astronomer the very day and the very hour at which 
the comet will reappear. He even indicates the very 
part of the heavens to which the telescope must be 
directed, in order to greet the wanderer on his return. 
When the time comes the astronomer finds that his 
friend has been a true prophet ; there is the comet on 
the expected day, and in the expected constellation. 

This happens again and again, so that the mathema- 
tician, with his pencil and his figures, marks stage by 
stage the progress of Encke through the years of his 
invisible voyage. At each moment he knows where the 
comet is situated, though utterly unable to see it. 

The joint labors of the two friends having thus dis- 
covered law and order in the movements of the comet, 
you may judge of their dismay when on one occasion 
Encke disappointed them. He appeared, it is true, but 
then he was a little late, and he was also not in the 
spot where he was expected. There was nearly being 
a serious difference between the two friends. The 
astronomer accused the mathematician of having made 
mistakes in his figures, the mathematician retorted that 
the astronomer must have made some blunder in his 
observations. A quarrel was imminent, when finally 
it was suggested to interrogate Encke himself, and see 
whether he could offer any explanation. The mathe- 



146 STAR-LAND. 

matician employed peculiar methods that I could not 
explain, so I shall transform his processes into a dia- 
logue between himself and the offending comet. 

"You are late," said he to the comet. "You have 
not turned up at the time I expected you, nor are you 
exactly in the right place ; nor, indeed, for that matter, 
are you now moving exactly as you ought to do. In 
fact, you are entirely out of order, and what explana- 
tion have you to give of this irregularity? " 

You see the questioner felt quite confident that there 
must have been some cause at work that he did not 
know of. Mathematicians have one great privilege; 
they are the only people in the world who never make 
any mistakes. If they knew accurately all the various 
influences that were at work on the comet, they could, 
by working out the figures, have found exactly where 
the comet would be placed. If the comet was not there, 
it is inevitable that there must have been something 
or other acting upon the comet, of which the mathe- 
matician was in ignorance. 

The comet, like every other transgressor, immedi- 
ately began to make excuses, and to shuffle off the 
blame on somebody else. " I was," said Encke, " going 
quietly on my rounds as usual. I was following out 
stage by stage the track that you know so well, and 
I would certainly have completed my journey and have 
arrived here in good time and in the spot where you 
expected me had I been let alone, but unfortunately I 
was not let alone. In the course of my long travels — 
but at a time when you could not have seen me — I 
had the misfortune to come very close to a planet, of 



THE COMET EXPLAINS. 147 

which I dare say you have heard — it is called Mer- 
cury. I did not want to interfere with Mercury; I 
was only anxious to hurry past and keep on my jour- 
ney, but he was meddlesome, and began to pull me 
about, and I had a great deal of trouble to get free 
from him, but at last I did shake him off. I kept my 
pace as well as I could afterwards, but I could not 
make up the lost' time, and consequently I am here a 
little late. I know I am not just where I ought to be, 
nor am I now moving quite as you expect me to do ; 
the fact is, I have not yet quite recovered from the bad 
treatment I have experienced." 

The astronomer and the mathematician proceeded 
to test this story. They found out what Mercury was 
doing ; they knew where he was at the time, and they 
ascertained that what the comet had said was true, and 
that it had come very close indeed to the planet. The 
astronomer was quite satisfied, and was proposing to 
turn to some other matter, when the mathematician 
said : — 

" Tarry a moment, my friend. It is the part of a 
wise man to extract special benefit from mishaps and 
disasters. Let us see whether the tribulations of poor 
Encke cannot be made to afford some very valuable 
information. We expected to find Encke here. Well, 
he is not here — he is there, a little way off. Let us 
measure the distance between the place where Encke 
is, and the place where he ought to have been." 

This the astronomer did. "Well," he said, "what 
will this tell you? It merely expresses the amount 
of delinquency on the part of Encke." 



148 STAR-LAM). 

"No doubt," said the mathematician, "that is so; 
but we must remember that the delinquency, as you 
call it, was caused by Mercury. The bigger and the 
heavier Mercury was, the greater would be his power 
of doing mischief, the more would he have troubled 
poor Encke, and the larger would be the derangement 
of the comet in consequence of the unfortunate inci- 
dent. We have measured how much Encke lias actu- 
ally been led astray. J lad Mercury been heavier than 
he is, that distance would have been larger; and if 
Mercury had been lighter than lie is, you would not, 
of course, have found so large an error in the 4 comet. t 

We may illustrate what is meant in this way. A 
steamer sails from Liverpool to New York, and in 
favorable circumstances the voyage across the Atlantic 
should be accomplished within a, week. But supposing 
that in the middle of the ocean a storm is encountered, 
by which the ship is driven from her course. She will, 
of course, be delayed, and her voyage will be length- 
ened. A trilling storm, perhaps, she will not mind, but 
a heavy storm might delay her six hours; a still greater 
storm might keep her back half a day; while cases are 
not infrequent in which the delay has amounted to one 
day, or two days, or even more. 

The delay which the ship has experienced may be 
taken as a measure of the vehemence of the storm. 1 
am not supposing that her machinery has broken down ; 
of course, thai sometimes happens at sea,, as do calamities 
of a far more tragic nature. I am merely supposing the 
ship to be exposed to very heavy weather, from which 
she emerges just as sound as she was when the storm 



THE COMET HELPS US TO WEIGH MERCURY. 149 

began. In such cases as this we may reasonably meas- 
ure the intensity of the storm by the number of hours' 
delay to which the passengers were subjected. " The 
weather we had was much worse than the weather you 
had," one traveller may say to another. " Our ship was 
two days late, while you escaped with a loss of one 
day." 

When the comet at last returned to the earth after 
a cruise of three years through space, the number of 
hours by which it was late expressed the vehemence 
of the storm it experienced. The only storm that the 
comet would have met with, at least in so far as our 
present object is concerned, was the trouble that it had 
with Mercury. The mass of Mercury was, therefore, 
involved in the delay of the comet. In fact, the delay 
was a measure of the mass of the planet. I do not 
attempt to describe to you all the long work through 
which the mathematician had to plod before he could 
ascertain the mass of Mercury. It was a very tedious 
and a very hard sum. but at last his calculations arrived 
at the answer, and showed that Mercury must be a light 
globe compared to the earth. In fact, it would take 
twenty-live globes, each equal to Mercury, to weigh as 
much as the earth. 

I dare say you will think that this was a very long 
and roundabout way of weighing. Supposing, however. 
we had to weigh a mountain, or rather a body which 
was bigger than fifty thousand mountains, and which 
was also many millions of miles away, all sorts of expe- 
dients would have to be resorted to. I have told you 
one of them. If vou feel any doubts as to the accuracy 



150 



STAR-LAND. 



with which such weighings can be made, then I must tell 
you that there are many other methods, and that these 
all agree in giving concordant results. 




Fig. 49. — Relative Weights of Mercury and the Earth. 

We hardly know anything as to what the globe of 
Mercury may be like. We can see little or nothing 
of the nature of its surface. We only perceive the 
planet to be a ball, brightly lighted by the sun, and we 
cannot satisfactorily discern permanent features thereon, 
as we are able to do on some of the other planets. 

THE PLANET VENUS. 



You will have no difficulty in recognizing Venus, but 
you must choose the right time to look out for her. In 
the first place, you need never expect to see Venus 



VENUS. 151 

very late at night. You should look for the planet in 
the evening, as soon as it is dark, towards the west, or 
in the morning, a little before sunrise, towards the east. 
I do not, however, say that you can always see Venus, 
either before sunrise or after sunset. In fact, for a 
large part of the year, this planet is not to be seen at 
all. You should therefore consult the almanac, and 
unless you find that Venus is stated to be an evening 
star or a morning star, you need not trouble to search 
for it. I may, however, tell you that Venus can never 
be an evening star and a morning star at the same time. 
If you can see it this evening after sundown, there is 
no use in getting up early in the morning to look out 
for it again. The planet will remain for several weeks 
a splendid object after sunset, and then will gradually 
disappear from the west, and in a couple of months 
later will be the morning star in the east. Venus 
requires a year and seven months to run through her 
changes, so that if you find her a bright evening star 
to-night, you may feel sure that she was a bright even- 
ing star a year and seven months ago, and that she will 
be a bright evening star in a year and seven months 
to come. Nor must you ever expect to see her right 
overhead ; she is always to the west or to the east. 

The splendor of Venus, when at her best, will pre- 
vent you at such times from mistaking this planet for 
an ordinary star. She is then more than twenty times 
as bright as any star in the heavens. The most conclu- 
sive proof, of the unrivalled brightness of Venus is 
found in the fact that she can be recognized in broad 
daylight without a telescope. Even on the brightest 



152 STAR-LAND. 

June afternoons the lovely planet is sometimes to be 
discerned like a morsel of white cloud on the perfect 
azure of the sky. 

Venus is so brilliant that perhaps you will hardly credit 
me when I tell you that she has no more light of her 
own than has a stone or a handful of earth, or a button. 
Is it possible that this is the case, you will say, for as 
we see the planet so exquisitely beautiful, how can she 
be merely a huge stone high up in the heavens ? The 
fact is that Venus shines by light not her own, but by 
light which falls upon her from the sun. She is lighted 
up just as the moon, or just as our own earth is lighted. 
Her radiance merely arises from the sunbeams which 
fall upon her. It seems at first surprising that mere 
sunbeams on the planet can give her the brillianc)^ that 
is sometimes so attractive. Let me show you an illus- 
tration which will, I trust, convince you that sunbeams 
will be adequate even for the glory of Venus. 

Here is a button. I hang it by a piece of fine thread, 
and when I dip it into the beam from the electric lamp, 
look at the brilliancy with which the mimic planet glit- 
ters. You cannot see the shape of the button ; it is too 
small for that ; you merely see it as a brilliant gem, 
radiating light all around. Therefore, we need not be 
surprised to learn that the brilliancy of the evening star 
is borrowed from the sun, and that if, while we are 
looking at the planet in the evening, the sun were to 
be suddenly extinguished, the planet would also vanish 
from view, though the stars would shine as before. 

Thus we explain the appearance of Venus. The 
evening star is a beautiful, luminous point, but it has 



HOW VENUS SHIXES. 153 

no shape which can be discerned with the unaided eye. 
When, however, the telescope is turned towards Venus 
we have the delightful spectacle of a tiny moon, which 
goes through its phases just as does our own satellite. 
When first seen as an evening star Venus will often be 
like the moon at the quarter, and then it will pass to 
the crescent shape. Then the crescent becomes grad- 
ually thinner, and next will follow a brief period of 
invisibility before the appearance of Venus as the morn- 
ing star. It seems at first a little strange that Venus 
when brightest should not be full like the moon, which 
in similar circumstances is, of course, a complete circle 
of light. The planet, however, has a very marked 
crescent-shaped form in these circumstances. But at 
this time the planet is so near us that the gain of bril- 
liancy from the diminution of distance more than com- 
pensates for the small part of the illuminated side which 
is turned towards us. 

You ought all to try to get some one to show you 
Venus through a telescope. A very large instrument 
is not necessary, and I feel sure you will be delighted 
to see the beautiful moon-shaped planet. You will then 
have no difficulty in understanding how the brightness 
of the planet has come from the sun. The changes in 
the crescent merely depend upon the proportion of the 
illuminated side which is turned towards us. Were 
Venus itself a sunlike body we should, of course, see 
no crescent, but only a bright circle of light. 

In Fig. 50 you will notice an imaginary picture of a 
young astronomer surveying Venus with a telescope. I 
have not, as is obvious, attempted to show the different 



L54 



STAB LAND. 



objects in their proper proportions* The sun is supposed 
bo have set, so thai his beams do not roach the astrono- 
mer. Night lias begun at his observatory ; but the 

sunbeams fall on Venus, and light her up on that side 




FlQ, 50. — To show that Wnus shinos by Sunlight. 

turned towards the sun. A part of this lighted side is, 
o( course, soon by the telescope which the astronomer 
is using, and thus the planet seems bo him like a ores- 
cent of light. 



THE TRANSIT OV VENUS. 



We might naturally think from Fig, 46 that Venus 

must pass at every revolution directly between the 
earth and the sun ; and therefore it might appear (hat 
what is called the transit of Venus across the sun ought 



THE TEANSIT OF VENUS. 155 

to occur every time between the appearance of the planet 
as the evening star and the next following appearance 
as the morning star. No doubt on each of these occa- 
sions Venus seems to approach the sun closely ; but the 

orbits of Venus and the Earth do not lie quite in the 
same plane, and hence the planet usually passes just 

over or just under the sun, so that it is a very rare 
event indeed for her to come right in front of the sun. 
But this does sometimes happen. It happened, for 

instances in the year L874, and again in the year 1882 ; 
but, alas ! I cannot- hold out to you the prospect of 

ever seeing another such spectacle. There will be no 
further occurrence of the transit of Venus until the 

year 2004, though there will be another eight years 
later, in 2012. 

It seems rather odd that one transit of Venus should 
be followed by another after an interval of eight years, 
and that then a period of much more than a century 
should have to elapse before there will be a repetition 
of a similar pair. This is in consequence of a, curious 
relation between the motion of Venus and the motion 
of the Earth, which I must endeavor to explain with 
the help o( a, Little illustration. 

Let us suppose a, clock with ordinary numbers round 
the dial, but so arranged that the slowly moving short 
hand requires 365.26 days to complete one revolution 
round the dial, while* the more rapidly moving long 
hand revolves in 224.70 days. The short hand will 
then go round once in a year, and the long' hand once 
during the revolution of Venus, Let us suppose that 

both hands start together from XII, then in 22-4.70 



15l> STAB LAND. 

days the long hand is round to XII again, but the short 
hand will have only advanced to about VII, and by the 
time it reaches XII the Long hand will have completed 
a largo part of a second circuit. It happens that the 
two numbers 224,70 and 365.26 are very nearly in the 
ratio of 8 to 13, In fact, if the numbers had only been 
*2i!4.8 and 365.3 respectively, they would be exactly in 
the proportion of 8 to 13, It, therefore, follows that 
eight revolutions of the short hand must occupy very 
nearly the same time as thirteen revolutions of the long 
hand. After eight years the short ham! will of course 
be found again at XII ; and at the same moment the 
Longhand will also be back at XII, after completing 
thirteen revolutions. 

We ean now understand why the transits, when they 
do occur, generally arrive in pairs at an interval o( eight 
years. Suppose that at a certain time Venus happens to 
interpose itself directly between the earth and the sun, 
then, when eight years have elapsed, the earth is, of 
course, restored for the eighth time since the first tran- 
sit to the same place, and Venus has returned to almost 
the same spot for the thirteenth time. The two bodies 
arfe practically in the same condition as they were at 
first, and, therefore, Venus again intervenes, and the 
planet is beheld as a black spot on the suifs surface. 
We must not push this argument too far: the relation 
between the two periods of revolution, though nearly, 
is not exactly S to 13, The consequence is that when 
another eight years have elapsed, the planet passes a 
little above the sun or a. little below the sun, and thus 
a third occurrence of the transit is avoided for more 



VENUS IN TRANSIT. 



157 



than a century. The next transit will take place at the 
opposite side of the path. 

We were fortunate enough to be able to see the 
transit of Venus in 1882 from Great Britain. Perhaps 
I should say a part of the transit, for the sun had set 
long before the planet had finished its journey across 




Fig. 51. — Venus in Transit across the Sun. 

the disk. Venus looked like a small round black spot, 
stealing in on the bright surface of the sun and gradu- 
ally advancing along the short chord that formed its 
track. 

An immense deal of trouble was taken in 1882, as 
well as in 1874, to observe this rare occurrence. Ex- 
peditions were sent to various places over the earth 
where the circumstances were favorable. Indeed, I do 
not suppose that there was ever any other celestial event 



158 STAR-LAND. 

about which so much interest was created. The reason 
why the event attracted so much attention was not 
solely on account of its beauty or its singularity ; it was 
because the transit of Venus affords us a valuable means 
of learning the distance of the sun. When observations 
of the transit of Venus made at opposite sides of the 
earth are brought together, we are enabled to calculate 
from them the distance of Venus, and knowing that, 
we can find the distance of the sun and the distances 
and the sizes of the planets. This is very valuable 
information ; but you would have to read some rather 
hard books on astronomy if you wanted to understand 
clearly how it is that the transit of Venus tells us all 
these wonderful things. I may, however, say that the 
principle of the method is really the same as that men- 
tioned on pp. 19-25. When you remember that not 
we ourselves, nor our children, and hardly our grand- 
children, will ever be able to see another transit of 
Venus, you will, perhaps, not be surprised that we tried 
to make the most of such transits as have occurred in 
our time. 

VENUS AS A WORLD. 

Though Venus exhibits such pretty crescents in the 
telescope, yet I must say that in other respects a view of 
the planet is rather disappointing. Venus is adorned 
by such a very bright dress of sunbeams that we can 
see but little more than those sunbeams, and we can 
hardly make out anything of the actual nature of the 
planet itself. We can sometimes discern faint marks 



VENUS AS A WORLD. 159 

upon the globe, but it is impossible even to make a 
conjecture of what the Venus country is like. This is 
greatly to be regretted, for Venus approaches compara- 
tively close to the earth, and is a world so like our own 
in size and other circumstances that we feel a legitimate 
curiosity to learn something more about her. 

But the marks on the planet, though very faint, are 
still sufficiently definite to have enabled some sharp- 
sighted astronomers to answer a question of much 
interest. They have made it plain that in one most 
important respect Venus is very unlike our Earth. Our 
globe, of course, rotates on its axis once each day. but 
Venus requires no less than 2:25 days to complete each 
rotation. In fact, this planet rotates in such a fashion 
that she always keeps the same face to the sun. The 
inhabitants of Venus will therefore find that it is per- 
ennial day on one side of this globe and everlasting 
night on the other. 

Venus is one of the few globes which might conceiv- 
ably be the abode of beings not very widely different 
from ourselves. In one condition especially — namely, 
that of weight — she resembles the earth so closely that 
those bodies which we actually possess would probably 
be adapted, so far as strength is concerned, for a resi- 
dence on the sister planet. Our present muscles would 
not be unnecessarily strong, as they would be on the 
moon, nor should we find them too weak, as they would 
certainly prove to be were we placed on one of the very 
heavy bodies of our system. Nor need the temperature 
of Venus be regarded as presenting any insuperable 
difficulties. She is. of course, nearer to the sun than 



160 STAR-LAND. 

we are, but then climate depends on other conditions 
besides nearness to the sun, so that the question as to 
whether Venus would be too hot for our abode could 
not be readily decided. The composition of the atmos- 
phere surrounding the planet would be the most material 
point in deciding whether terrestrial beings could live 
there. I think it to be in the highest degree unlikely 
thai the atmosphere of Venus should chance to suit us in 
the requisite particulars, and therefore I think there is 
not much likelihood that Venus is inhabited by any 
men, women, or children resembling those on this 
earth. 

THE PLANET MAKS AND HIS MOVEMENTS. 

The path of the earth lies between the orbits of the 
planets Venus and Mars. It is natural for us to en- 
deavor to learn what we can about our neighbors. We 
ought to know something, at all events, as to the people 
who live next door to us on each side. I have, how- 
ever, already said that we cannot observe very much 
upon Venus. The case is very different with respect to 
Mais. He is a, planet which we are fortunately enabled 
to study minutely, and he is full of interest when we 
examine him through a good telescope. 

The right season for observing Mars must, of course, 
be awaited, as he is not always visible. Such seasons 
recur about every two years, and then for months 
together Mars will be a brilliant object in the skies 
every night. Nor has Mars necessarily to be sought in 
the early morn or immediately after sunset, in the 



MARS, THE RUDDY PLANET. 161 

manner we have already described for Venus and 
Mercury. At the time Mars is at his best he comes 
into the highest position at midnight, and he can 
generally be seen for hours before, and be followed for 
hours subsequently. You may, however, find some diffi- 
culty in recognizing him. You probably would not at 
first be able to distinguish Mars from a fixed star. No 
doubt this planet is a ruddy object, but some stars are 
also ruddy, and this is at the best a very insecure char- 
acteristic for identification. 1 cannot give you any 
more general directions, except that you should get 
your papa to point out Mars to you- the next time it is 
visible. It is just conceivable that papa himself might 
not know how to find Mars. If so, the sooner he gets 
a set of star maps and begins to teach himself and to 
teach you, the better it will be for you both. 

Mars, though apparently so like a star, differs in 
some essential points from any star in the sky. The 
stars proper are all fixed in the constellations, and 
they never change their relative positions. The groups 
which form the Great Bear or the Belt of Orion do not 
alter, they are just the same now as they were centuries 
ago. But the case is very different with a planet such 
as Mars. The very word planet means a wanderer, and 
it is justly applied, because Mars, instead of staying 
permanently in any one constellation, goes constantly 
roaming from one group to the other, lie is a very 
restless body: sometimes he pays his respects to the 
heavenly Twins, and is found near Castor and Pollux 
in Gemini, then he goes off and has a brief sojourn with 
the Bull, but it looks as if that tierce animal erol tired 



It)-! STAB LAND. 

of his company* and hunted him oft to the Lion. His 
quarters then become still more critical. Sometimes it 
looks as it he desired to seek tor peace beneath the 
waters, and so he visits Aquarius, while at other times 
he is found in dangerous proximity to the claws of the 
Crab. 

Mars cannot even make up his mind to run steadily 
round the heavens in one direction; sometimes he will 
bolt off rapidly; then pause for a. while, and turn back 
again; then the original Impulse will return, and he 
will resume his journey in the direction ho at first 
intended. It is no wonder that I am not able to give 
you very explicit directions as to how you may secure 

a sight of a truant whose wanderings are apparently so 
uncertain. Vet there is a definite order underlying all 
his movements. Astronomers, who make it their busi- 
ness to study t he movements of Mars, can follow him 
on his way; they know exactly where he is now, and 
where he will be every night for years and years to 
come. The people who make the almanacs come (o the 

astronomers and get hints from them as to what Mars 
intends to do, so that the almanacs announce the posi- 
tions in which the planet will be found with as much 
regularity as it he was in the habit of behaving with 
the orderly propriety of the sun or the moon. 

We must not lay all the blame on Mars for the 
eccentricities of his movements. Our earth is to a very 
large extent responsible. What we think to be Mars' 
vagaries are often to be explained by the fact, that we 
ourselves on the earth are rapidly shifting about, and 

altering our point of view. 



WHY MARS SEEMS ERRATIC, 



L63 



1 was driving down a pretty country road with a 
Little girl three years old beside me, when I was 
addressed with the little remark, wk Look at the tree 
going about in the field." Now, you or I, with our 
Longer experience of the world around us, know that it 
is not the custom of trees to take themselves up and 







Fig, 52. — How the Tree seems to move about. 



walk about the fields. But this was what this little 
girl saw, or rather what she thought she saw : and very 
often what we do see is something very different from 
what we think we see. We think we see Mars per- 
forming all these extraordinary movements, as the little 
girl thought she saw the tree moving about. But just 
as that little girl, when she grew to be a big girl, found 
that what she thought was a tree walking across the 
field must really have some quite different explanation, 
SO we, too, find that what Mars seems to do is one thing, 
and what Mars actually does is quite another thing. 
Let us see what the little erirl noticed. She was 



1()4 STAR-LAND. 

looking at the tree, and first she saw it on one side of 
the house, and then she saw it on the opposite side (Fig. 
52). If it had been a cow instead of a tree, of course 
the natural supposition would have been that the cow 
had walked. Our little friend may, perhaps, have 
thought it unusual for a tree to walk, but still she saw 
the undoubted fact that the tree had shifted to the 
other side of the house, and therefore, perhaps, remem- 
bering what the cow could do, she said the tree had 
moved. 

The little girl did not stop to reflect that she herself 
had entirely changed her position, and hence arose the 
surprising phenomenon of a tree that could move about. 




Fiq. 53. — A Specimen <>r the Track of Mars. 

Yon will understand this, at once, from the two positions 
of the car here shown. In the first position, as the girl 
looks at the tree, the dotted line shows the direction 
of her glance, and the other dotted line shows how the 
apparent places of the tree and the house 1 have altered. 
It is her change of place that has accomplished the 
transformation. Observe also that the tree appeared to 
her to move in the direction opposite to that in which 
she is going. 

Mars generally appears to move round among the 
stars from west to east. In fact, if we were viewing 



MARS AND HIS PATH. 165 

him from the sun lie would always seem to move in 
this manner. But at certain seasons our earth is mov- 
ing- very fast past Mars, and this will make him appear 
to move in the opposite direction. This apparent 
motion is sometimes so much in excess of his real 
motion, that it may give us an entirely incorrect idea 
of what the planet is actually doing. 

Thus, notwithstanding that Mars is moving one way, 
he may appear to us who dwell on the earth to be going 
in the opposite way. This illusion only happens for a 
short time, just when we arc passing Mars, as we do 
every two years. The effect on the planet is to make 
the path he pursues at this time something like that 
shown in Fig. 53. The planet is nearest to us at the 
time he is moving in this loop. He is then to be seen 
at his best in the telescope, so that it is especially inter- 
esting to watch Mars through this critical part of his 
career. 

I want to show you how to make a little calculation 
which will explain the law by which the seasons when 
we can sec Mars best will follow each other. The period 
he requires for a voyage round the sun is not quite two 
years, for that would be 730 days, and Mars only takes 
l>87 days for his journey. It is, however, true that 1^|- 
years is very nearly the period of Mars, Hence, every 
o*2 years Mars will complete 17 rounds. From this we 
shall be able to sec how long it will take after the earth 
once passes Mars before they pass again. I shall sup- 
pose there is a circular course, around which two boys 
start together to run a race. One of these boys is such 
a good runner that he will get quite round in 17 min- 



166 STAR-LAND. 

utes ; but the other boy can hardly run more than half 
as quickly, for he will require 32 minutes to complete 
one circle. Here then is the question. Suppose the 
two boys to start together : how long will it be before 
the faster runner gains one complete circuit on the 
other? By the time the good runner (A) has com- 
pleted one circuit, the bad runner (B) has only got a 
little more than halfway. When A has completed his 
second circuit, he has, of course, run for twice 17 min- 
utes — that is, for 34 minutes. This is two minutes 
longer than the time B requires to get round once ; 
therefore B is only ahead by a distance which A could 
cover in about one minute ; but B will have advanced 
during this minute a distance for which A will require 
another half-minute, during which B covers a distance 
for which A will need a further quarter, and so on. 
But all these intervals — one minute, half a minute, a 
quarter of a minute, one-eighth, one-sixteenth, and so 
on — added together amount to two minutes, and hence 
it follows that B will not be overtaken until about two 
minutes after A has completed his second round — that 
is, in 36 minutes altogether. 

We can pass from this illustration to the case of the 
planet Mars and the earth. The orbit of the earth is 
traversed in a year, and therefore, after the earth has 
once passed Mars, which is then, as astronomers would 
say, in opposition, about two years and the eighth of a 
year — that is, two years and six or seven weeks — will 
elapse before Mars is again favorably placed. You will 
thus see that we need not expect to observe Mars under 
the best conditions every year. Besides, the distance 



THE ELLIPSE. 



167 



of the planet from the earth at opposition varies so 
greatly that some oppositions are more favorable than 
others. 

The time has come when I must tell you something 
about the shapes of the paths in which the earth and 
the other planets perform their great journeys round 
the sun. Perhaps you will think that I am going to 
contradict some of the things that I have told you 
before. I have often represented the orbits of the plan- 
ets as circles, and now I am going to tell you that this 




Fig. 54. — How to draw an Ellipse. 

is not correct. The fact is that the paths are nearly 
circles ; but, still, there is some departure from the 
exact circular shape. Mars, in particular, moves in a 
path which is more different from a circle than the path 
of the earth, and consequently it is appropriate to intro- 
duce this subject when we are engaged about Mars. 
We must first take another lesson in drawing, and 



168 



STAR-LAND. 



the appliances I want you to use for the purpose are 
very simple. You must have a smooth board and some 
tacks or drawing-pins, besides paper, pencil, and twine. 
We first lay a sheet, of paper on the board, and then 
put in two tacks through the paper and into the board. 




Fig. 55. — Specimens of Ellipses. 



It does not much matter where we put them in. Next 
we take a piece of twine and tie the two ends together 
so as to form a loop, which we pass round the two tacks 



THE IMPORTANCE OF THE ELLIPSE. 169 

(Fig. 54). In the loop I place the pencil, and then jon 
see I move it round, taking care to keep the twine 
stretched. Thus I produce a pretty curve, which we 
call the ellipse. I must ask all of you to practise this 
experiment. Try with different lengths of string, and 
try using different distances between the tacks. Here 
are some sketches of two shapes of ellipse and a parab- 
ola (Fig. 55). Elliptic curves can be made almost cir- 
cles by putting the two tacks close together, or they 
can be made very long in comparison with their width. 
They are all pretty and graceful figures, and are often 
useful for ornamental work. The ellipse is a pretty 
shape for beds of flowers in a grass-plot. 

The importance of the ellipse to astronomers is 
greater than that of any other geometrical figure. In 
fact, all the planets, as they perform their long and 
unceasing journeys round the sun, move in ellipses ; 
and though it is true that these ellipses are very nearly 
circles, yet the difference is quite appreciable. 

It is also important to observe that the sun is not 
in the centre of the ellipse which the planet describes. 
The sun is nearer to one end than to the other. And 
the actual position of the sun must be particularly 
noted. Suppose that some mighty giant were preparing 
to draw an exact path for the earth, or for Mars, of 
course he would want to have millions of miles of string 
for producing a big enough curve, and one of the nails 
that he used would have to be driven right into the 
sun. The following is the astronomer's more accurate 
method of stating the facts. He calls each of the 
points represented by the tacks around which the string 



170 STAR-LAND. 

is looped a, focus of the ellipse ; the two points together 
are said to be the foci; and as the planet is describing 
its orbit, the position of the sun will lie exactly at one 
of the foci. 

The ellipse is a curve that nature is very fond of 
reproducing. From an electric light, a brilliant beam 
will diverge. If you hold a globe in the beam, and let 
the shadow fall on a sheet of paper, it forms an ellipse. 
If you hold the sheet squarely, the shadow is a circle ; 
but as you incline it, you obtain a beautiful oval, and by 
gradually altering the position, you can get a greatly 
elongated curve. Indeed, you can thus produce an 
ellipse of almost any form. The electric light is not 
indispensable for this purpose ; any ordinary bright 
lamp with a small flame will answer, and by taking 
different sized balls and putting them in various posi- 
tions, you can make many ellipses, great and small. 

THE DISCOVERIES MADE BY TYCHO AND KEPLER. 

It was by the observations of a celebrated old 
astronomer, named Tycho Brahe, that the true shape 
of a planet's path came to be afterwards determined. 
Tycho lived in days before telescopes were invented. 
He had few of the excellent contrivances for measuring 
which we have in our observatories. We shall take a 
look at this fine old astronomer, as he sits amid his 
curious astronomical machines. 

He lived on air island near Copenhagen, and he has 
given us a picture of himself (Fig. 56), as he is seated 
with his quaint apparatus, and his assistants around 



TYCHO BRAHE IN HIS OBSERVATORY. 171 

QVADRANS MVRALI$ 

SIVE TICHONICUS. 




Fig. 56. — Tycho Brahe in his Observatory. 



172 STAR-LAND. 

him, busily engaged in observing the heavens. You 
see the walls of his observatory are decorated with pic- 
tures ; and one of the great Danish hounds which the 
King of Denmark had presented to him lies asleep at 
his feet. I do not think we should now encourage big 
dogs in the observatory at night. Nor do modern as- 
tronomers put on their velvet robes of state, as Tycho 
was said to have done when he entered into the pres- 
ence of the stars, as, by so doing, he showed his respect 
for the heavens. Astronomers, nowadays, rather prefer 
to wear some comfortable coat which shall keep out 
the cold, no matter what may be its appearance from 
the picturesque point of view. In this wonderful con- 
trivance, you see Tycho Brahe did not use any actual 
telescope. He observed through a small opening in the 
wall, and lest there should be any mistake as to what 
is going on, you see he is pointing towards it, and giving 
his three assistants their instructions. The most im- 
portant work is being done by the man on the right. 
He is engaged in making the actual observation. But 
he has no aid from magnifying lenses. All he can do 
is to slide a pointer up or down till it is just in line 
with the planet or star as he sees it through the hole 
opposite. 

On the circle a number of marks have been engraved, 
and there are numbers placed opposite to the marks ; it 
is by these that the position of the object is to be ascer- 
tained. If the object is high, then the pointer will be 
low ; and if the object is low, then the pointer will 
be high. The observer calls out the position when he 
has found it, and there, you see, is a man ready with 



AN ANCIENT ASTRONOMER. 173 

writing materials to take down the observation. Notice 
also the other astronomer who is looking at the clock. 
He gives the time, which must also be recorded accu- 
rately. In fact, the entire process of finding the place 
of a heavenly body consists in two observations — one 
from the circle and the other from the clock ; so that 
though Tycho had no telescope to aid his vision, yet 
the principle on which his work was done was the same 
as that which we use in our observatories at this 
moment. 

You may think that such a concern would hardly be 
capable of producing much reliable work. However, 
Tycho compensated in a great degree for the imperfec- 
tion of his instrument by the skill with which he used 
it. He had a noble determination to do his very best. 
Perseverance will accomplish wonders even with very 
imperfect means. A great astronomer has said that 
a skilful observer ought to be able to make valuable 
measurements with a common cart-wheel ! 

It was with instruments on the principle of that 
which I have here shown that Tycho made his cele- 
brated observations of Mars. Week after week, month 
after month, year after year, did the patient old 
astronomer track the planet through his capricious 
wanderings. 

Before we try to explain anything, it is of -course 
necessary to ascertain, with all available accuracy, 
what the thing actually is. Therefore, when we seek 
to explain the irregular movements of a planet, the 
first thing to be done is to make a careful examination 
of the nature of those irregularities. And this was 



174 STAR-LAND. 

what Tycho strove to do with the best means at his 
disposal. 

The full benefit of Tycho's work was realized by 
Kepler when he commenced to search out the kind of 
figure in which Mars was moving. First he tried vari- 
ous circles, and then he sought, by placing the centre 
in different positions, to see whether it would not be 
possible to account thus for the irregularities of the 
wayward planet. It would not do ; the movement was 
not circular. This was thought very strange in those 
days, for the circle was regarded as the only perfect 
curve, and it was considered quite impossible for a 
planet to have any motion except it were the most per- 
fect. There was, however, no help for it ; so Kepler 
sagaciously tried the ellipse, which he considered to 
be the most perfect curve next to the circle. He con- 
tinued his long calculations, until at last he succeeded 
in finding one particular ellipse, placed in one particu- 
lar position, which would just explain the strange wan- 
derings of our erratic neighbor. It was not alone that 
the motion of the planet traced out an ellipse ; it was 
further discovered that the sun lies at one of the foci 
of the curve. If the sun were anywhere else, the 
motion of the planet would have been different from 
that which Tycho had found it to be. 

You must know that this discovery is one of the very 
greatest that have ever been made in the whole extent 
of human knowledge. After it had been proved that 
the orbit of Mars was elliptic, it became plain that the 
same path must be traced by every planet. There are 
very big planets, and there are small ones ; there are 



THE ENGINE-DRIVER AND THE PLANET. 175 

planets which move in very large orbits, and there are 
planets whose paths are comparatively small. In all 
cases the high road which the planet follows is invari- 
ably an ellipse, and the sun is invariably to be found 
situated at the focus. It is surely interesting to find 
that these beautiful ellipses which we can draw so sim- 
ply with a piece of twine and a pencil should be also 
the very same figures which our great earth and all the 
other bodies which revolve around the sun are ever 
compelled to follow. 

Kepler also made another great discovery in con- 
nection with the same subject. If the planet moved in 
a circle with the sun in the centre, then there would be 
very good reason to expect that it would always move 
at the same speed, for there would be no reason why it 
should go faster at one place than at another. In fact, 
the planet would then be revolving always at the same 
distance from the sun, and every part of its path would 
be exactly like every other part. But when we consider 
that the motion is performed in an ellipse, so that the 
planet is curving round more rapidly at the extremities 
of its path than in the other parts where the curvature 
is less perceptible, we have no reason to expect that 
the speed shall remain the same all round. 

We know that the engine-driver of a railway train 
always has to slacken speed when he is going round a 
sharp curve. If he did not do so, his train would be 
very likely to run off the line, and a dreadful accident 
would follow. The engine-driver is well aware that 
the conditions of pace are dependent on the curvature 
of his line. The planet finds that it, too, must pay 



176 STAR-LAND. 

attention to the curves ; but the extraordinary point is 
that the planet acts exactly in the opposite way to the 
engine-driver. The planet puts on its highest pace at 
one of the most critical curves in the whole journey. 
There are two specially sharp curves in the planet's 
path. These are, of course, the two extremities of the 
ellipse which it follows. The cautious engine-driver 
would, of course, creep round these with equal care, 
and no doubt the planet goes slowly enough about that 
end of the ellipse which is farthest from the sun. There 
its pace is slower than anywhere else ; but from that 
moment onwards the planet steadily applies itself to 
getting up more and more speed. As it traverses the 
comparatively straight portion of the celestial road, the 
pace is ever accelerating until the sharp curve near 
the sun is being approached ; then the velocity gets 
more and more alarming, until at last, in utter defiance 
of all rules of engine-driving, the planet rushes round 
one of the worst parts of the orbit at the highest possible 
speed. And yet no accident happens, though the planet 
has no nicely laid lines to keep it on the track. 

If lines are necessary to save a railway train from 
destruction, how can we possibly escape when we have 
no similar assistance to keep us from flying away from 
the sun and off into infinite space ? Kepler has taught 
us to measure the changes in the speed of the body 
with precision. He has shown that the planet must, 
at every point of its long journey, possess exactly the 
right speed ; otherwise everything would go wrong. I 
dare say you have seen, at different points along a line 
of railway, boards put up here and there, with notices 



THE EARTH'S PATH. 177 

like, " Ten miles an hour." These words are, of course, 
an intimation to the engine-driver that he is not to vary 
from the speed thus stated. Kepler has given us a law 
which is equivalent to a large number of caution boards, 
fixed all round the planet's path, indicating the safe 
speed for the journey at every stage. It is fortunate 
for us that the planet is careful to observe these regu- 
lations. If the earth were to leave her track, the 
consequences would be far worse than those of the 
most frightful railway accident that ever happened. 
Whichever side we took would be almost equally dis- 
astrous. If we went inwards we should plunge into 
the sun, and if we went outwards we should be frozen 
by cold. 

We owe our safety to the care with which the speed 
of the earth is prescribed. When near the sun, the earth 
is pulled inwards with exceptionally strong attraction. 
We are often told that when a strong temptation seizes 
us, the wisest thing that we can do is to run away as 
hard as possible. This is just what the laws of dynamics 
cause the earth to do at this critical time. She puts 
on her very best pace, and only slackens when she has 
got well away from the danger. 

The peril that we are exposed to when the earth is 
at the other end of the orbit is of an opposite character. 
We are then a long way from the sun, and the pull 
which it can exercise upon the earth is correspondingly 
lessened. Care is then required lest we should escape 
altogether from the sun's warmth and his guidance. 
We must therefore give time to the sun to exercise his 
power, so as to enable the earth to be recalled; accord- 



178 STAR-LAND. 

ingly we move as slowly as posssible until the sun con- 
quers the earth's disposition to fly off, and we begin to 
return. 

You may remember that when we were speaking 
about the moon, I showed you how a body might 
revolve around the earth in a circle under the influence 
of an attraction towards the earth's centre. So long as 
the path is really a circle, then the power with which 
the earth is drawing the body remains the same. In a 
precisely similar way, a body could revolve around the 
sun in a circle, in which case also the attraction of the 
sun will remain the same all round. But now we have 
a very much more difficult case to consider. If the 
body does not always remain at the same distance, the 
power of the sun will not be the same at the different 
places. Whenever the object is near the sun, the 
attraction will be greater than when it is farther off. 
For example, when the distance between the two bodies 
is doubled, then the pull is reduced to the fourth part 
of what it was before. 

THE DISCOVERIES MADE BY NEWTON. 

I have now some great discoveries to talk to you 
about, which were made by Sir Isaac Newton. He was 
not an astronomer who looked much through a tele- 
scope, though he made many remarkable experiments. 
He used to sit in his study and think, and then he used 
to draw figures with his pencil, and make long calcu- 
lations. At last he was able to give answers to the 
questions : What is the reason why the planet moves 



DISCOVERIES BY NEWTON. 179 

in an ellipse ? Why should it move in this curve 
rather than in any other? Why should this ellipse 
be so placed that the sun lies at one of the foci? 

If the planet had run uniformly round its course, 
Newton would have found his task an impossible one. 
But I have already explained that the motion is not 
uniform. I described how the planet hurried along 
with extra speed a^ certain parts of its path ; how it 
lingered at other parts ; how, in fact, it never preserved 
the same rate for even a single minute during the whole 
journey. Kepler had shown how to make a time-table 
for the whole journey. In fact, just as a captain on 
a long voyage keeps a record of each day's run, and 
shows how to-day he makes 170 miles, and to-morrow 
perhaps 200, and the next day 210, while the day after 
he may fall back to 120, so Kepler gave rules by which 
the log of a planet in its voyage round the sun might 
be so faithfully kept that every day's run would be 
accurately recorded. 

When Newton commenced his work, one of the first 
questions he had to consider was the following : Sup- 
pose that a great globe like a planet, or a small globe 
like a marble, or an irregular body like an ordinary 
stone, were to be thrown into space, and were then to 
be left to follow its course without any force whatever 
acting upon it, where would it go to ? 

You may say, at once, that a body under such cir- 
cumstances will presently fall down to the ground ; 
and so, of course, it will, if it be near the earth. I am 
not, however, talking of anything near the earth ; I 
want you to imagine a body far off in the depths of 



180 STAR-LAND. 

space, among the stars. Such a body need not neces- 
sarily fall down here, for you see the moon does not fall, 
and the sun does not. 

If you were at a great distance from our globe and 
from all other large globes — so far, indeed, that their 
attractions were imperceptible — you could try the 
experiment that I wish now to describe. Throw a stone 
as hard as ever you can, and what will happen ? Of 
course, when you do it down here, it moves in a pretty 
curve through the air, and tumbles to the ground ; but 
away in open space, what will the stone do? There 
will be no such motion as up or down, as we ordinarily 
understand it ; for though the earth, no doubt, will lie 
in one particular direction at a great distance, yet there 
will be other bodies just as large in other directions ; 
and there is no reason why the stone should move 
towards one of these rather than to another ; in fact, if 
they are all far enough, as the stars are from us, their 
attractions will be quite inappreciable. There is, there- 
fore, not the slightest reason why the stone should 
swerve to one side more than to another. There is no 
more reason why it should turn to the right than why 
it should turn to the left. Nor could you throw the 
stone so as to make it follow a curved path. You can, 
of course, make it describe a curve while it remains in 
your hand, but the moment the stone has left your 
hand, it proceeds on its journey by a law over which 
you have no control. As the direction cannot be changed 
towards one side more than towards the other, the stone 
must simply follow a straight line from the very moment 
when it is released from your hand. 



A LESSON FROM A STONE. 181 

The speed with which the stone is started will also 
not change. You might at first think that it would 
gradually abate, and ultimately cease. No doubt a 
stone thrown along the road will behave in this way, 
but that is because the stone rubs against the ground. 
If you throw a stone across a sheet of ice, then it will 
run a very long distance before it stops, and all the 
time it will be moving in a straight line. In this case 
there is but little loss by rubbing against the ice, because 
it is so smooth. Thus we see that if the path be exceed- 
ingly smooth, the body will run a long way before it 
stops. Think of the distance a railway train will run 
if, while travelling at full speed along a level line, the 
steam is turned off. 

These illustrations all show that if you let a body 
alone, after having once started it, and do not try to 
pull it this way or that way, and do not make it rub 
against things, that body will move on continually in a 
straight line, and will keep up a uniform speed. We 
can apply this reasoning to a stone out in space. It 
would certainly move in a straight line,, and would go 
on and on forever, without losing any of its pace. 

I need hardly tell you that no one has ever been able 
to try this experiment. In the first place, we reside 
upon the surface of the earth, and we have no means of 
ascending into those elevated regions where the stone 
is supposed to be projected. There is also another dif- 
ficulty which we cannot entirely avoid, and that arises 
from the resistance of the air. All movements down 
here are impeded because the body has to force its way 
through the air ; and in doing so it invariably loses 



182 



STAR-LAND. 



some of its speed. Out in open space there is, of 
course, no air, and no loss of speed can therefore arise 
from this cause. 

There are, however, several actual experiments by 
which we can assure ourselves of the general truth. Set 
a humming-top spinning (Fig. 57) ; it gradually comes 
to rest, partly because of the rubbing of its point on the 

table, and partly because it 
has to force its way through 
the air. In fact, the hum of 
the top that you hear is only 
produced at the expense of its 
motion. Supposing I use a 
much heavier top ; if I set it 
spinning it will keep up for 
many minutes, because its 
weight gives it a better store 
of power wherewith to over- 
come the resistance of the air. 
I remember hearing a story 
about Professor Clerk-Maxwell. He had, when at Cam- 
bridge, invented one of these large and heavy tops, which 
would spin for a long time. One evening the top was 
left spinning on a plate in his room when his friends 
took their departure, and no doubt it came to rest in due 
time. Early the next morning, Professor Maxwell, 
hearing the same friends coming up to his rooms again, 
jumped out of bed, set the top spinning, and then got 
back to bed, and pretended to be asleep. He thus 
astounded his friends, who, of course, imagined that 
the top must have been spinning all the night long ! 




Fig. 57. — The Humming-top. 



THE FIRST LAW OF MOTION. 183 

If we spin a top under the receiver of an air pump 
(Fig. 58), it will keep up its motion for a very much 
longer time after the air has been exhausted than it 
would in ordinary circumstances. Such experiments 
prove that the motion of a body will not of itself natu- 



Fig. 58. — To illustrate the First Law of Motion. 

rally die out, and that if we could only keep away the 
interfering forces altogether, the motion would continue 
indefinitely with unabated speed. What I have been 
endeavoring to illustrate is called the first law of motion. 
It is written thus : — 

" Every body continues in its state of rest or of uni- 
form motion in a straight line, except in so far as it may 
be compelled by impressed forces to change that state" 

I would recommend you to learn this by heart. I 
can assure you it is quite as well worth knowing as 



184 STAR-LAND. 

those rules in the Latin Grammar with which many of 
you, I have no doubt, are acquainted. The best proof 
of the first law of motion is derived, not from any 
experiments, but from astronomy. We make many 
calculations about the movements of the sun, the moon, 
the stars, and then we venture on predictions, and we 
find those predictions verified. Thus we had a transit 
of Venus across the sun in 1882, and every astronomer 
knew that this was going to occur, and many went to 
the ends of the earth so that they might see it favor- 
ably. Their anticipations were realized ; they always 
are. Astronomers make no mistakes in these matters. 
They know that there will be another transit of Venus 
in the year 2004, but not sooner. The calculations by 
which these accurate prophecies are made involve this 
first law of motion ; and as we find that such prophecies 
are always fulfilled, we know that the first law of motion 
must be true also. 

Newton knew that if a planet were merely left alone 
in space, it Avould continue to move on forever in a 
straight line. But Kepler had shown that the planet 
did not move in a straight line, but that it described an 
ellipse. One conclusion was obvious. There must be 
some force acting upon the planet which pulls it away 
from the straight line it would otherwise pursue. We 
may, for the sake of illustration, imagine this force to 
be applied by a rope attached to the planet so that at 
every moment it is dragged by some unseen hand. To 
find the direction this rope must have, we take the law 
of Kepler, which explains the rules according to which 
the planet varies its speed. I cannot enter into the 



NEWTON'S DISCO VEKIES. 185 

question fully, as it would be too difficult for us to dis- 
cuss now. I should have to talk a great deal more about 
mathematics than would be convenient just at pres- 
ent ; but I think you can all understand the result to 
which Newton was led. He showed that the rope must 
always be directed towards the sun. In other words, 
suppose that there was no sun, but that in the place 
which it occupied there was a strong enough giant con- 
stantly pulling away at the planet, then we should find 
that the speed of the planet would alter just in the way 
it actually does. Thus we learn that some force must 
reside in the sun by which the planet is drawn, and 
this force is exerted, although there is no visible bond 
between the sun and the planet. 

There is another fact to be learned about the sun's 
attraction, and this time we obtain it by knowing the 
shape of the curve followed by the planet. The laws 
by which the planet's speed is regulated prove that the 
force emanates from the sun. We shall now learn 
much more when we take into account that the path 
of the planet is an ellipse, of which the sun lies at 
the focus. Nothing has been said as yet regarding the 
magnitude of the pull which is being exerted by the 
sun. Is that pull to be always the same, or is it to be 
greater at some times than at other times ? Newton 
showed that no ellipse other than a circle could be 
described, if the pull from the sun were always the 
same. Its magnitude must be continually changed, 
and the nearer the planet lies to the sun, the more 
vehement is the pull it receives. Newton laid down 
the exact law by which the force on the planet at any 



186 STAR-LAND. 

one place in its path could be compared with the force 
at any other position. Let us suppose that the planet 
is in a certain position, and that it then passes into a 
second position, which is twice as far from the sun. 
The pull upon the planet at the shorter distance is not 
only greater than the pull at the longer distance, but 
it is actually four times as much. Stating this result 
a little more generally, we assert, in the language of 
astronomers, that the attraction varies inversely as the 
square of the distance. If this law were departed from, 
then I do not say that it would be impossible for the 
planet to revolve around the sun in some fashion, but 
the motion would not be performed in an ellipse described 
around the sun in the focus. 

You see how very instructive are the laws which 
Kepler discovered. From the first of them we were 
able to infer that the sun attracts the planets; from 
the second, we have learned how the magnitude of the 
attracting force varies. 

The true importance of these great discoveries will 
be manifest when we compare them with what we have 
already learned with regard to the movements of the 
moon. As the moon revolves around the earth it is 
held by the earth's attraction, and the moon follows a 
path which, though nearly a circle, is really an ellipse. 
This orbit is described around the earth just as the 
earth describes its path around the sun. That law by 
which a stone falls to the ground in consequence of the 
earth's attraction is merely an illustration of a great 
general principle. Every body in the whole universe 
attracts every other body. 



TWO BIG CANNON-BALLS. 187 

Think of two weights lying on the table. They no 
doubt attract each other, but the force is an extremely 
small one — so small, indeed, that you could not meas- 
ure it by any ordinary appliance. One or both of the 
attracting masses must be enormously big if their 
mutual gravitation is to be readily appreciable. The 
attraction of the earth on a stone is a considerable 
force, because the eafth is so large, even though the 
stone may be small. Imagine a pair of colossal solid 
iron cannon-balls, each 53 yards in diameter, and weigh- 
ing about 417,000 tons. Suppose these two globes were 
placed a mile apart, the pull of one of them on the other 
by gravitation would be just a pound weight. Notwith- 
standing the size of these masses, the hand of a child 
could prevent any motion of one ball by the attraction 
of the other. If, however, they were quite free to move, 
and there was absolutely no friction, the balls would 
begin to draw together; at first they would creep so 
slowly that the motion would hardly be noticed. The 
pace would no doubt continue to improve slowly, but 
still not less than three or four days must elapse before 
they will have come together. 

By the kindness of Professor Dewar, I am enabled to 
exhibit a contrivance with which we can illustrate the 
motion of a planet around the sun. Here is a long wire 
suspended from the roof of this theatre, and attached 
to its lower end is an iron ball, made hollow for the 
sake of lightness. When I draw the ball aside, it 
swings to and fro with the regularity of a great pen- 
dulum. But when I place a powerful magnet in its 
neighborhood (Fig. 59), you see that as soon as the 



188 



STAB LAM). 



ball gets near the magnet it is violently drawn to one 
side, and follows a curved path. This magnet may be 
taken to represent the sun, while tin* ball is like our 




Fig. :»«.). The Effect of Attraction 



earth, or any other planet, which would move in a 

straight line were it not for the attraction of the sun 

which draws the body aside. 



THE GEOGRAPHY OF MARS. 

We will now say something with respect to fche 
geography of our fellow-planet, a subject which seems 

all the more interesting because Mars is so like the 

earth in many respects. We require a fairly good tele- 
scope for the purpose o( seeing him well, but when 

such an instrument is directed to the planet, a beau- 



VIEWS OF MARS. 



189 




tit'ul picture of another world is unfolded (Fig, 60). 
There are many things visible on his surface, but we 
must always remember that even with our most power- 
ful telescopes the planet still appears a long way o\)\ 



190 



STAR-LAND. 





Fig, 1. June L3, 1894, lGh. 1 
Lori£. 165°. Diam. Wfi. Seeing 



Fig. 2. July 23, 1894, 17h. 1? 
Long. Km Diam. l2 // .02. Seeing 




Fig. 3. Jul v 29/1894, lOh. 07m. 




Fii,. 4, Auk. 11 



jLong.70°, Diaim lS^J. Seeing- J in LQ. Long. 338°. Diam. U".8. S< 

-■-•■■'■ ! ___ 

Fig. 61. — Mars. 

(By Douglass, Lowell Observatory.) 

In the most favorable circumstances, Mars is at least 
one hundred times as far from us as the moon. But 
we know that an object on the moon must be as large 



THE GEOGRAPHY OF MARS. 191 

as St. Paul's Cathedral if it is to be visible in our tele- 
scopes. An object on Mars must be, therefore, at least 
one hundred times as broad and one hundred times 
as long as St. Paul's Cathedral if it is to be discern- 
ible by astronomers on our earth. We can, therefore, 
only expect to see the general features of our fellow- 
planet. Were we looking at our earth from a similar 
distance, and with equally good telescopes, the conti- 
nents and oceans, and the larger seas and islands, would 
all be large enough to be conspicuous. It is, however, 
doubtful whether they could ever be properly revealed 
through the serious impediment to vision which our 
atmosphere would offer. 

It fortunately happens that the surface of Mars is 
only obscured by clouds to a very trifling extent, and 
we are thus able to see a panorama of our neighboring 
globe laid before us. Mars is not nearly so large as our 
earth, the diameters of the two bodies being nearly as 
two to one. It follows that the number of acres on the 
planet is only a quarter of the number of acres on the 
earth. Careful telescopic scrutiny shows that the chief 
features which we see on Mars are of a permanent char- 
acter. In this respect Mars is much more like the moon 
than the sun. The latter presents to us merely glow- 
ing vapors, with hardly more permanence than is pos- 
sessed by the clouds in our own sky. On the other 
hand, the entire absence of clouds from the moon 
enables us to see the permanent features on its surface. 
Most of the visible features on Mars are also invariable ; 
though, occasionally it would seem that the climate pro- 
duces some changes in its appearance. 



192 STAR-LAND. 

We first notice that there are differently colored 
parts on Mars. The darkish or bluish regions are 
usually spoken of as seas or oceans ; though we should 
be going beyond our strict knowledge were Ave to 
assert that water is actually found there. Look at the 
horn-shaped object in the centre of the lower picture 
in Fig. 60. We call it the Kaiser Sea, and it is so 
strongly marked that even in a small telescope it can 
be often seen. You must not, however, always expect to 




Fig. 02. — The South Pole of Mars, September, 1S77 (Green). 

notice this feature when you look at the planet through 
a telescope, for it turns round and round. We can make 
a globe representing Mars. On this are to be depicted 
this great sea and the other characteristic objects. But 
as we turn the globe around, the opposite side of the 
planet is brought into view, and other features are 
revealed like those represented in the upper figure. 
Mars requires 24 hours 37 minutes 22.7 seconds to 
complete a single rotation. It is somewhat remarkable 
that this only differs from the earth's period of rotation 
by a little more than half an hour. 



POLAR SNOWS OX MARS. 193 

Mars contains what we call continents as well as 
oceans, and we also find there lakes and seas and 
straits. These objects are indicated in the drawings 
that are here represented. But the most striking fea- 
tures which the planet displays are the marvellous 
white regions, which are seen both at its North Pole 
and at its South Pole (Fig. 62). If we were able to 
soar aloft above our earth and take a bird's-eye view of 
our own polar regions, we should see a white cap at the 
middle of the arctic circle. This appearance would be 
produced by the eternal ice and snow. It would in- 
crease during the long, dark winter, and be somewhat 
reduced by melting during the continuously bright 
summer. Though we cannot thus see our earth, yet 
we can sometimes observe one Pole of Mars and some- 
times the other, and we find each of these Poles crowned 
with a dense white cap, which increases during the 
severity of its winter, and which declines again with 
the w^armth of the ensuing summer. 

Sketches of Mars have been made by many astron- 
omers ; among them we may mention Mr. Green, who 
made a beautiful series of pictures at Madeira in 1877. 
These may be supplemented by the drawings of Mr. 
Knobel in 1884, when the opposite Pole of the planet 
was turned to view. The drawings show the polar snows. 
and there seem to be some elevated districts in his arctic 
regions which retain a little patch of snow after the main 
body of the ice cap has shrunk within its summer limits. 
An interesting case of this kind is shown in Fig. 62, 
which has been copied from one of Mr. Green's drawings. 

It has lately been surmised that the continents on 



194 



STAR LAND. 



Mars are occasionally inundated by Hoods of water. 
There are also indications of clouds banging over the 

Martian lands, but the inhabitants of that planet, in 
this respect, escape much better than we do. A certain 
amount of atmosphere always surrounds Mars, though 
it is much less copious than that we have here. As to 
the composition of this atmosphere we know nothing. 
For anything we can tell, it might be a gas so poison- 
ous that a single inspiration would be fatal to us ; or if 

it contained oxygen in much larger proportion than our 
air does, it- might be fatal from the mere excitement to 
our circulation which an over-supply of stimulant would 

produce. I do not think it the least, likely that our 
existence could be supported on Mars, even if we could 
get there. We also require certain conditions of cli- 
mate, which would probably be totally different from 
those we should find on Mars. 

Many remarkable observations of Mais have been 

lately made by Mr. Percival Lowell. It seems very 

doubtful how far our former division of continents and 
Oceans On Mars can be maintained. Mr. Lowell has 
paid Special attention to a wonderful system of lines 
on the planet's surface to which the name of "canals" 
has been given, which often show such a degree of reg- 
ularity as would almost suggest/ the idea, that, they had 
been laid down by intelligent guidance. 

THE SATELLITES OF MARS. 



When Mill's appeared in his full splendor in 1S77, 
he was for the first lime honored with the notice of 



THE PLANETS 1 FAMILIES. 195 

instruments capable of doing him justice. I do not, 
however, mean that in former apparitions he was not 
also carefully observed, but a great improvement had 
recently taken place in telescopes, and it was thus under 
specially favorable auspices that his return was wel- 
comed in 1S77. This year will be always celebrated 
in astronomical history for a beautiful discovery made 
by Professor Asaph Hall, the illustrious astronomer at 
Washington. 

Before I can explain what this discovery was, I must 
have a little talk about moons, or satellites as they are 
often called. You know that we have one moon, which 
is constantly revolving round the earth, and accompa- 
nies the earth in its long voyage round the sun. Hut 
the earth is only a planet, and there are many other 
planets which are worlds like ours. It is natural to 
compare these worlds, and as we have one moon, why 
should not the other planets also have moons? If there 
are children in one house in a square, why should there 
not be children in the other houses? We find that 
some of the other planets have satellites, but they do 
not seem to be distributed very regularly. In fact, they 
are almost as capriciously allotted as the children 
would be in eight houses that you .might take at 
random. 

In N timber One there lives an old bachelor, and in 
X umber Two a single lady. These are Mercury and 
Venus, and of course there are no children in either of 
these houses. Number Three is inhabited by old mother 
Earth, and she has got a tine big son, called the Moon. 
Number Four is a nice little house inhabited by Mars. 



196 



STAK-LAND, 



There are to be found a pair of little twins, and nimble 
creatures they are too. Number Five is a great man- 
sion. A very big man lives here, called Jupiter, with 
four robust sons and daughters that everybody knows. 



Deimos 




• 
* 

/ 
/ 

/ 
/ * 


Phobos 


V 

s 
N 

\ . 
\ 
rvj 

\ 

V 


kjJ-Urfv ,< V IWWwBPr yWB ^ETaH IB 


/ ^ • ■*■ 

/ 


o* Bo* A \ 


\ 
\ 
. \ 
\ 


t fd 

m 


THE \fl 

PLANET HI 


\ 
\ 

1 
i 

1 


« ^1 


MARS EM 


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1 

1 
I 




J21 7 h*** , , 


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i in 30 fc* 8 \- 


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Fig. 63. 



Mars and his Two Satellites. 



I fancy they must go to many dancing parties, for every 
night they may be seen whirling round and round. For 
three hundred years these four moons have been known 
to astronomers, but in 1892 there was an addition to 
the family in the shape of a tiny moon which had never 
been seen up to that time. Number Six is also a fine 
big house, though not quite so big as Number Five, but 
larger than any of the others. It is inhabited by Saturn, 



MARS AND HIS SATELLITES. 197 

and contains the biggest family of all. Up till the 
other day eight sons and daughters were known to live 
here, but they are not nearly so sturdy as Jupiter's 
children ; in fact, the young Saturns do not make much 
display, and some of them are so delicate that they are 
hardly ever seen. In this household, too, a new member 
has recently appeared. For fifty years the family was 
known to consist of these eight sons and daughters, but 
in August, 1898, when they were being photographed 
in a group, it was discovered that a ninth moon had 
been added. Number Seven is also a line large house ; 
but Uranus, who lives there, is such a recluse that 
unless you carefully keep your eye on his house, you 
will hardly ever catch a glimpse of him. There are 
four children in that house, I believe, but we hardly 
know them. They move in circles of their own, and 
apparently have seen a good deal of trouble. Only one 
more house is to be mentioned, and that is Number 
Eight, inhabited by Neptune. It contains one child, 
but we are hardly on visiting terms with this household, 
and we know next to nothing about it. 

Before 18TT, Mars appeared to be in the same condi- 
tion as Venus or Mercury — that is, devoid of the dig- 
nity of attendants. There was, however, good reason 
for thinking that there might be some satellites to Mars, 
only that we had not seen them. You see that, as Num- 
ber Three had one child, and Numbers Five, Six, Seven, 
and Eight had each one, or more than one, it seemed 
hard that poor Number Four should have none at all. 
It was, however, certain that if there were any satellites 
to Mars, they must be comparatively small things ; for 



198 STAB LAM). 

it' Mars had even one considerable moon, it must have 
been discovered Long ago, 

On bhe memorable occasion in L877, Professor Hall 
discovered that the ruddy planet Mars was attended, 
not alone by one moon, but by two. Their behavior 
was most extraordinary. It appeared to him at first 
almost as it' one of these little moons was playing at 
hide-and-seek. Sometimes it would peep out at one 

side of the planet, and sometimes at the other side. 
I have here a picture (Fig, 68) which shows how these 

moons o( Mars revolve. That is the globe of the planet 

himself in the middle, and he is turning round steadily 
in a period which is nearly the same as our day. But 

the remarkable point is that the Inner of the moons of 
Mars runs round the planet in T hours 89 minutes. It 

would seem very strange in our sky if we had a. little 

moon which rose in the west instead of in the east, and 

which galloped right across the heavens three times 

every day and this is what Mars has. The Outer moon 

takes a more Leisurely journey, for he requires 80 hours 
IS minutes to complete a circuit. If for no other reason 
than to see these wonderful moons, it would be very 
interesting to visit Mars. 
The satellites of this planet are in contrast to our 

moon. In the first place, our moon takes 27 days to gO 
round the earth, and is comparatively a long way oi'L 
The moons of Mars Eire much nearer to their planet, 
and they gO round mneh more qniekly. There is also 
another difference, The moons of Mars are mneh 
smaller bodies than OUT moon. If we represent. Mars 
by a good-sized football, his moons, on the same seale, 



A SUPERB TELESCOPE REQUIRED, 199 

would be hardly so big as the smallest-sized grains of 
shot. Does it not speak well for the power of telescopes 

in those modern days that objects so small as the satel- 
lites of Mars should be seen at all? You remember, of 
course, that neither Mars himself nor his moons have 
any Light of their own. They shine solely in eonse- 
quenee of the sunlight which falls upon them. They 
are merely lighted like the earth itself, or like the 
moon. The difficulty about observing the satellites is 
all the greater because they are seen in the telescope 
elose to such a brilliant body as Mars. The glare from 
the bright planet is such that when we want to see 
faint objects like the satellites we have to hide Mars, so 
as to get a comparatively dark spaee in which to search. 
Now that they know exactly what to look for, a 
good many astronomers have observed the satellites of 
Mars. A superb telescope is nevertheless required. 
And, in faet, you could not find a better test for the 
excellence of an instrument than to try if it will show 
these delieate objects. Hut do not imagine that merely 
having a good telescope and a clear sky is all that is 
requisite for making astronomical discoveries, You 
might just as well say that by putting a first-rate 
cricket-bat in any man's hands will ensure his making a 
grand seore. Every boy knows that the bat does not 
make the erieketer, and I can assure him that neither 
will the teleseope make the astronomer. In both eases, 
no doubt, there is some element of luck. But of this 
you may be certain: that as it is the man that makes 
the seore, and not the bat, so it is the astronomer that 
makes the discovery, and not his teleseope. 



'200 



STAB LAM). 



Deimos and Phobos were the names of the two per- 
sonages, according to Homer, whoso duty it was to 
attend on the god Mars, and to yoke his steeds. A 
conclave of classical scholars and astronomers appropri- 
ately decided thai Deimos and Phobos must be the 
names of the two satellites to the planet which boars 
the name o( Mars. 

HOW THE TELESCOPE AIDS IN VIEWING FAINT 
OBJECTS, 



\W have been hitherto talking about Large planets, 

which, if hot as big as our earth, aro at loasl as big as 

our moon. But now we have to say a few words about 
a number of Little planets, many of them being so very 

small thai a million rolled together would not form a 

globe so big as this earth* These Little objects von 
cannot see with your unaided eye, and even with a tele- 
scope they only look Like very small stars. 

I have often been asked why it is that a telescope 

enables ns to see objects, both Taint and small, which 

our unaided eyes fail to show. Perhaps this will be 

a £oo(\ opportunity to say a tew words on the subject. 
I think we can explain the utility o\' the telescope by 
examinihg our own eyes. The eye undergoes a remark- 
able transformation when its owner passes from darkness 
into a brilliantly Lighted room (Fig, 64). Here you see 
two views of an eye, and you notice the great difference 
between them. They are not intended to be the eyes 
of two different people, or the two eyc^s of the same 
person; they are merely two conditions o I the same eye. 



THE TELESCOPE AND THE EYE. 



201 



They are intended to illustrate two different states of 
the eye of a collier. The right shows his eye when he 
is above ground in bright daylight; the left is his eye 
when he has gone down the coal-pit to his useful work 
in the dark regions below. I remember when I went 
down a coal-pit I was lowered down a long shaft, and 
when the bottom was reached a safety lamp was handed 
to me. The gloom was such, that at first I found some 
little difficulty in guiding my steps, but the capable 




This shows the Eye in 
the Dark. 



~r 



Fig. 64. 




This shows the Eye in 
the Daylight. 



guide beside me said in an encouraging voice, " You 
will be all right, sir, in a few moments, for you will get 
your pit-eyes" I did get my " pit-eyes," as he promised, 
and was able to see my way along sufficiently to enjoy the 
wonderful sights that are met with in the depths below. 
The change that came over my eyes is that which 
these two pictures illustrate : the black, round spot in 
the centre is an opening covered with a transparent 
window, by which light enters the eye ; the black spot 
is called the pupil, and nature has provided a beautiful 
contrivance by which the pupil can get larger or smaller, 
so as to make vision agreeable. When there is a great 
deal of light we limit the amount that enters by con- 



202 STAB LAND. 

trading the pupil so as to make the opening smaller. 
Thus the picture with the small pupil represents the 

state of the collier's eye when he is above ground in 
bright sunlight. When he descends Into the pit, where 

the light is very scanty, then he wants to grasp as much 
of it as ever he can, and consequently his pupil enlarges 
so as to make a wider opening, and this is what he calls 
getting his wk pit-eyes." 

J^ut you need not go down a coal-mine to see the 
use of the iris — for so thai pretty membrane is called 
which surrounds the pupil. Every time you pass from 
light into darkness the same thing can be perceived. 

When we turn down the lights in a room, so that we are 
in comparative darkness, our pupils gradually expand. 

As soon as the lights are turned up again, then our 
pupils begin to contract. Other animals have the same 
contrivance in their eyes. You may notice in the 
Zoological Gardens how quickly the pupil of the lion 
contracts when he raises his eyes to the light. The 

power of rapidly changing the pupil might be of service 
to a, beast of prey. Imagine him crouching in a, dense 
shade to wait for his dinner; then of course the pupil 
Avill be large from deficiency of light; but when lie 
Springs out suddenly on his victim, in bright light, it 
WOUld surely be of advantage to him to be able at once 

to see clearly. Accordingly his pupil adjusts itself to 
the altered conditions with a rapidity that might not 

be necessary for creatures of less predaceous habits. 

These changes of the pupil explain how the telescope 
aids our eyes when we want to discern any faint objects, 

like the little planets. Such bodies arc not visible to 



THE CHANGES OF THE PUPIL. 208 

the unaided eyes, beoause our pupils are not Large 
enough to grasp sufficient Light for the purpose. Even 
when they are opened to the utmost, we want something 
that shall enable them to open wider still. We must 
therefore borrow assistance from some device which 
shall have an effect equivalent to an enlargement of 
the pupil beyond the Limits that nature has actually 
assigned io it. What we waul is something Like a 
funnel which shall transform a Large beam o( rays into a 

small one. I may explain what I mean by the follow- 
ing illustration: Suppose that it is raining heavily, and 
that you want to till a, bucket with water. It' you 
merely put the bucket out in the middle of a field, it 
will never be filled; but bring it to where the rain-shoot 

from a house-top is running down, and then your bucket 

will be running over in a tew moments. The reason, 

of course, is that the broad top of the house has caught 

a vast number of drops and brought them together in 

the narrow shoot, and st> the bucket is filled. In the 

same way the telescope gathers the rays o( light that 
fall on the object glass, and condenses them into a small 
beam which can enter the eye. We thus have what is 
nearly equivalent io an eye with a pupil as big as the 

object glass. Thus the effect of a grand telescope 
amounts to a practical increase of the pupil from the 

size of a threepenny-piece up to that of a dinner-plate, 

or even much Larger still. 

THE ASTEROIDS OB small PLANETS. 

An asteriod is Like a tiny star, and in fact the two 
bodies are very often mistaken. If we could get closi^ 



204 STAR-LAND. 

to the objects, we should see a wide difference between 
them. We should find the asteroid to be a dark planet 
like our earth, lighted only by the rays from the sun. 
The star, small and faint though it may seem, is itself a 
bright sun, at such a vast distance that it is only visible 
as a small point. The star is millions of times as far 
from us as the planet, and utterly different in every 
respect. 

It is a curious fact that the planets should happen to 
resemble the stars so closely. We can find an analogous 
fact in quite another part of nature. In visiting a good 
entomological collection, you will be shown some of 
the wonderful leaf-like insects. These creatures have 
wings, exactly formed to imitate leaves of trees, with 
the stalks and veins completely represented. When 
one of these insects lies at rest, with its wings folded, 
among a number of leaves, it would be almost impos- 
sible to penetrate the disguise. This mimicry is no 
doubt an ingenious artifice to deceive the birds or other 
enemies that want to eat the insect. There is, however, 
one test which the cunning bird could apply: the 
leaves do not move about of their own accord, but the 
leaf-insects do. If therefore the bird will only have 
the patience to wait, he will see a pair of the seeming 
leaves move, and then the deception will be to him a 
deception no longer, and he will gobble up the poor 
insect. 

In our attempts to discover the planets we experi- 
ence just the same difficulties as the insect-eating bird. 
Wide as is the true difference between a planet and a 
star, there is yet such a seeming resemblance between 



PLANETS AND STARS. 205 

them that we are often puzzled to know which is which. 
The planets imitate the stars so successfully, that when 
one of them is presented to us among myriads of stars 
it is impossible for us to detect the planet by its appear- 
ance. But we can be cunning — we can steadily watch, 
and the moment we find one of these star-like points 
beginning to creep about we can pounce upon it. We 
know by its movements that it is only disguised as a 
star, but that it is really one of the planets. 

It is not always easy to discover the asteriods even 
by this principle, for unfortunately these bodies move 
very slowly. If you have a planet in the field of 
view, it will creep along so gradually that an hour or 
more mast have elapsed before it has shifted its posi- 
tion with respect to the neighboring stars to any appre- 
ciable extent. The search for such little planets is 
therefore a tedious one, but there are two methods of 
conducting it: the new one, which has only recently 
come into use, and the old one. I shall speak of the 
old one first. 

Although the body's motion is so slow, yet when 
sufficient time is allowed, the planet will not only move 
away from the stars close by, but will even journey 
round the entire heavens. The surest way of making 
the discovery is to study a small part of the heavens 
now and to examine the same locality again months or 
years afterwards. Memory will not suffice for this pur- 
pose. No one could recollect all the stars he saw with 
sufficient distinctness to be confident that the field of 
the telescope on the second occasion contained either 
more or fewer stars than it did on the first. The only 



206 STAR-LAND. 

way of doing this work is to draw a map of the stars 
very carefully. This is a tedious business, for the stars 
are so numerous that even in a small part of the heavens 
there will be many thousands of stars visible in the 
telescope. All of these will have to be entered faith- 
fully in their true places on the map. When this has 
been done the map must be laid aside for a season, and 
then it is brought out again and compared with the sky. 
No doubt the great majority of the objects will be found 
just as they were before. These are the stars, the dis- 
tant suns, and our concern is not at present with them. 
Sometimes it will happen that an object marked on the 
first map has left a vacant place on the second. This, 
however, does not help us much, for, whatever the 
object was, it has vanished into obscurity, and a new 
planet could hardly be discovered in this way. But 
sometimes it will happen that there is a small point of 
light seen in the second map which has no correspond- 
ing point in the first. Then, indeed, the expectation of 
the astronomer is aroused ; he may be on the brink of a 
discovery. Of course he watches accurately the little 
stranger. It might be some star that had been acci- 
dentally overlooked when forming the map, or it might 
possibly be a star that has become bright in the interval. 
But here is a ready test : is the body moving ? He 
looks at it very carefully, and notes its position with 
respect to the adjacent stars. In an hour or two his 
suspicions may be confirmed ; if the object be in motion, 
then it is really a planet. A few further observations, 
made on subsequent days, will show the path of the 
body. And the astronomer has only to assure himself 



HOW TO FIND OUT PLANETS. 207 

that the object is not one of the planets that have been 
already found before he announces his discovery. 

The new method of searching for small planets, 
which has only come into use in recent years, is a very 
beautiful one, and renders the process of making such 
discoveries much more easy than the older method 
which I have just described. 

We can take photographs of the heavenly bodies by 
adjusting a sensitive plate in the telescope so that the 
images of the objects we desire to see shall fall upon 
it. The method will apply to very small stars, if by 
excellent clockwork and careful guiding we can keep 
the telescope constantly pointing to the same spot until 
the stars have had time to imprint their little images. 
Thus we obtain a map of the heavens, made in a thor- 
oughly accurate manner. Indeed, the delicacy of pho- 
tography for this purpose is so great, that the plates 
show many stars which cannot be seen with even the 
greatest of telescopes. Suppose that a little planet 
happened to lie among the stars which are being photo- 
graphed. All the time that the plate is being exposed 
the wanderer is, of course, creeping along, and after an 
hour (exposures even longer are often used), it may 
have moved through a distance sufficient to ensure its 
detection. The plate will, therefore, show the stars 
as points, but the planet will betray its presence by 
producing a streak. 

The asteroids now known number between 400 and 
500. Out of this host a few afford some information 
to the astronomer, but the majority of them are objects 
possessing individually only the slightest interest. No 



208 STAR LAND, 

small planet Is worth Looking at as a telescopic picture. 
We should consider that asteroid to be a Large one 
which possessed a surface altogether as great as Eng- 
land or France. Many of these planets have a super- 
ficial extent not so Large as some of our great counties. 
A globe which was just big enough to be covered by 
Yorkshire if you could imagine that Large county 
neatly folded round it would make a very respectable 

minor planet. 

We know hardly anything of the nature of these 
small worlds, hut it is certain that any Living beings 
they could support must have a. totally different nature 
from the creatures that we know on this earth. We 

can easily prove this by making a calculation. I shall 
suppose a small planet one hundred miles wide, its 
diameter being, therefore, the one-eightieth part of the 

diameter of the earth. If we were landed on such a, 

globe, we should he far more puzzled by the extraordi- 
nary Lightness of everything than we should he in the 
similar case of the moon to which I referred (p. L24), 
If we suppose the planet to be constructed of materials 

which had the same density as those of which the earth 

is made, then every weight would be reduced to the 

eightieth part i)\' what it is here. 

There would be one curious consequence of resi- 
dence on such a globe. We have heard o( attempts to 
make flying machines, or io provide a man with wings 
by which he shall soar aloft like the birds. All such 

contrivances have hitherto failed. It may he possible 

to make a, pair of wings by which a, man can fly down, 

hut. it is quite another matter when he tries to fly up 



LAWN TENNIS ON FLORA. 209 

again. Suppose, however, we wore living on a small 
planet, it would be perfectly easy to fly, for as our 
bodies would only seem to weigh a couple of pounds, 
we ought to be able to flap a pair of wings strong 
enough to overcome so trivial a (owe. I should, how- 
ever, add that this is on the supposition that the atmos- 
phere has the same density as our own. 

Life on these small planets would indeed be ex- 
traordinary. Let us take, for example, Flora, and 
see how a game o( lawn tennis on that body would be 
managed. The very slightest blow of the raeket would 
drive the ball a, prodigious distance before it could 
touch the ground : indeed, unless the courts were about 
Kalf a mile long, it would be impossible to serve any 
ball that was not a fault. Nor is there any great exer- 
tion necessary for playing lawn tennis on Flora, even 
though the courts are several hundred acres in extent. 
As a young lady ran to meet the ball and return it, 
each of her steps might eover a hundred yards or so 
without extra effort : and should she have the misfor- 
tune to get a fall, her descent to the ground would be 
as gentle as if she was seeking repose on a bed of the 
softest swan's-down. 

These little planets cluster together in a certain part 
of our system. Inside are the four inner planets, of 
which we have already spoken ; outside are the four 
outer planets, of which we have soon to speak. Be- 
tween these two groups there was a vacant space. It 
seemed unreasonable that where there was room for 
planets, planets should not be found. Accordingly the 
search was made, and these objects were discovered. 



210 STAR-LAND. 

Even at the present day, more and more are being 
constantly added to the list. 

Up till quite recently all the small planets which 
had been discovered confined themselves to the space 
lying between the paths of the major planets Mars and 
Jupiter. This invariable rule was, however, departed 
from in the case of one of these bodies which was dis- 
covered in August, 1898. This little body, which was 
known for some time by tlu 4 provisional appellation of 
I) Q, and which has now been definitely christened 
Eros, is an exception to this rule. It travels at an 
average distance from the sun actually less than that 
of Mars, and at the nearest point can come within 
15,000,000 miles of the earth. 

We occasionally get information from these little 
bodies ; for in their revolutions through the solar sys- 
tem, they sometimes pick up scraps of useful knowledge, 
which we can elicit from them by careful examination. 
For example, one of the most- important problems in the 
whole of astronomy is to determine the sun's distance. 
I have already mentioned one of the ways of doing this, 
which is given by the 4 transit of Venus. Astronomers 
never like to rely on a single method ; we are therefore 
glad to discover any other means of solving the same 
problem. This it, is which the little planets will some- 
times do for us. Juno on one occasion approached very 
close to the earth, and astronomers in various parts of 
the globe observed her at the same time. When they 
compared their observations they measured the sun's 
distance. But T am not going to trouble you now with 
a matter so difficult. Suffice it to say, that for this, as 



THE LESSER MEMBERS OF OUB SYSTEM. -11 

for all similar investigations, the observers were eon- 
strained to use the very same principle as that which 
we illustrated in Fig, 5, 

Let me rather close this lecture with the remark that 
we have here been considering only the lesser members 
of the great family which circulate round the sun, and 
that we shall speak in our next lecture of the giant 
members of our system. 



LECTURE IV. 

JUPITER, SATURN, URANUS, NEPTUNE. 

Jupiter, Saturn, Uranus, Neptune -Jupiter — The Satellites o( Jupiter 
Saturn— The Nature of the Rings William Herschel The l>is- 
covery of Uranus The Satellites of Uranus The Discovery of 
Neptune. 

Our lecture to-day ought to make us take a very 
humble view of the size o( our earth. Mercury, Venus, 
and Mars may be regarded as the earth's peers, though 
we arc slightly Larger than Venus, and a good deal 
Larger than Mercury or Mars ; but all these tour globes 
are insignificant in comparison with the gigantic planets 
which Lie iu the outer parts of our system. These 
great bodies do not enjoy the benefits of the sun to the 
same extent that we are permitted to (\o ; they are so 
far off that the sun's rays become greatly enfeebled 
before they can traverse the distances but the gloom 
of their situation seems to matter but little, lor it is 
highly improbable thai any of these bodies could be 
inhabited. 

A view o[' parts of the paths of these Tour great. 
planets is shown in Fig. 65. The innermost is Jupiter, 
which completes a circuit in about twelve years; then 
comes Saturn, revolving in an orbit SO great that 
twenty-nine years and a half are required before the 

complete journey is finished. Still further outside is 
Uranus, which has a. Longer journey than Saturn, and 

212 



THE GREAT PLANETS; 213 

moves so much more slowly that a man would have 
to live to the ripe old age of eighty-four it' a complete 
revolution of Uranus was to be accomplished during 
his Lifetime. At the boundary of our system revolves 



- c Neptune 



'*wiS- 



B*i 



ears 



- -...Uranus 



nOS 



*a<r* .Saturn 



Jupiter.. 



<C* Mars *, 



Ku;. 65, The Orbits of the Four Giant Planets. 

the planet Neptune, and though it is a mighty globe, 

yet we cannot see it without a telescope. It is invisible 
to the naked eye for two reasons : first of all, because 
it is so far from the sun that the light which illuminates 
it is excessively feeble ; and, secondly, because it is so 
far from us that whatever brilliancy it has is largely 
reduced. 



214 STAR-LAND. 

JUPITER. 

Of all these bodies Jupiter is by far the greatest; 
he is, indeed, greater than all the other planets rolled 
into one. The relative insignificance of the earth when 
compared with Jupiter is well illustrated by the fact 
that if we took 1200 globes each as big as our earth, 
and made them into a single globe, it would only be 




eQ 



Fig. 66. — Jupiter and the Earth compared. 

as large as the greatest of the planets. A view of the 
comparative sizes of the earth and Jupiter is shown in 
Fig. 66. 

Fig. 67 shows a picture of Jupiter as seen through 
the telescope. First, you will notice that the outline of 
the planet's shape is not circular, for it is plain that the 
vertical diameter in this picture is shorter than the 
horizontal one ; in fact, Jupiter is flattened at the Poles 
and bulges out at the equator, so that a section through 
the Poles is an ellipse. Jupiter is turning round rapidly 
on his axis, and this will account for the protuberance. 



JUPITER'S CLOUDS. 215 

We find that the planet has assumed almost the same 
form as if it were actually a liquid. This we can 
illustrate by a globe of oil which is poised in a mixture 
of spirits of wine and water so carefully adjusted that 
the oil has no tendency to rise or fall. As we make 




Fig. 67. — The Clouds of Jupiter. 

the globe of oil rotate, which we can easily do by pass- 
ing a spindle through it, we see that it bulges out in the 
form that Jupiter as well as other planets have taken. 

On the picture of the planets you will see shaded 
bands. These are constantly changing their aspect, and 
for a double reason. In the first place, they change 
because Jupiter is rotating so quickly that in five hours 
the whole side of the planet which is towards us has 



216 STAK-LAND. 

been carried out of sight. In another five hours the 
original side of the globe will be back again, for the 
entire rotation occupies about 10 hours, or, more pre- 
cisely, 9 hours 55 minutes 21 seconds. 

But these bands are themselves not permanent objects. 
They have no more permanence than the clouds over 
our own sky. Sometimes Jupiter's clouds are more 
strongly marked than on other occasions. Sometimes, 
indeed, they are hardly to be seen at all. It is from 
this we learn that those markings which we see when 
we look at the great planet are merely the masses of 
cloud which surround and obscure whatever may con- 
stitute his interior. 

There is a circumstance which demonstrates that 
Jupiter must be an object exceedingly different from 
the earth, though both bodies agree in so far as having 
clouds are concerned. What would you think when I 
tell you that we were able to weigh Jupiter by the aid 
of his little moons, of which I shall afterwards speak ? 
These little bodies inform us that Jupiter is about 300 
times as heavy as our earth, and we have no doubt 
about this, for it has been confirmed in other ways. 
But we have found by actual measurement that Jupiter 
is 1200 times as big as the earth, and therefore, if he 
were constituted like the earth, he ought to be 1200 
times as heavy. This is, I think, quite plain ; for if 
two cakes were made of the same material, and one 
contained twice the bulk of the other, then it would 
certainly be twice as heavy. If there be two balls of 
iron, one twice the bulk of the other, then, of course, 
one has twice the weight of the other. But if a ball 



WHERE DOES JUPITER'S HEAT COME FROM? 217 

of lead have twice the bulk of a ball of iron, then the 
leaden ball would be more than twice as heavy as the 
iron, because lead is the heavier material. In the same 
way, the weights of the earth and Jupiter are not what 
we might expect from their relative sizes. If the two 
bodies were made of the same materials and in the 
same state, then Jupiter would be certainly four times 
as heavy as we find him to be. We are, therefore, led 
to the belief that Jupiter is not a solid body, at least 
in its outer portions. The masses of cloud which 
surround the planet seem to be immensely thick, and 
as clouds are, of course, light bodies in comparison with 
their bulk, they have the effect of largely increasing the 
apparent size of Jupiter, while adding very little to his 
weight. There is thus a great deal of mere inflation 
about this planet, by which he looks much bigger than 
his actual materials would warrant if he were consti- 
tuted like the earth. 

These facts suggest an interesting question. Why 
has Jupiter such an immense atmosphere, if we may 
so call it? The clouds we are so familiar with down 
here on the earth are produced by the heat of the sun, 
which beats down upon the wide surface of the ocean, 
evaporates the water, and raises the vapor up to where 
it forms the clouds. Heat, therefore, is necessary for 
the formation of cloud ; and with clouds so dense and so 
massive as those on Jupiter, more heat would apparently 
be necessary than is required for the moderate clouds 
on this earth. Whence is Jupiter to get this heat? 
Have we not seen that the great planet is far more 
distant from the sun than we are ? In fact, the intensity 



218 STAR-LAND. 

of the sun's heat on Jupiter is not more than the twenty- 
fifth part of what we derive from the same source. We 
can hardly believe that the sun supplied the heat to 
make those big clouds on the great planet ; so we must 
cast about for an additional source, which can only be 
inside the planet itself. So far as his internal heat is 
concerned, Jupiter seems to be in much the same con- 
dition now as our earth was once, ages ago, before its 
surface had cooled down to the present temperature. 
As Jupiter is so much larger than the earth, he has 
been slower in parting with his heat. The planet 
seems not yet to have had time to cool sufficiently to 
enable water to remain on his surface. Thus the inter- 
nal heat of the planet supplies an explanation of his 
clouds. We may also remark that as the present con- . 
dition of Jupiter illustrates the early condition of our 
earth, so the present condition of the earth foreshadows 
the future reserved for Jupiter when he shall have had 
time to cool down, and when the waters that now exist 
in the form of vapor shall be condensed into oceans on 
his surface. 

THE SATELLITES OF JUPITER. 

Every owner of a telescope delights to turn it on the 
planet Jupiter, both for the spectacle the globe itself 
affords him, and for a view of the wonderful system of 
moons by which the giant planet is attended. Fortu- 
nately the four satellites of Jupiter lie within reach of 
even the most modest telescope, and their incessant 
changes relative to Jupiter and each other give them a 



THE MOONS OF JUPITER. 219 

never-ending interest for the astronomer. Compared 
with the torpid performance of our moon, which requires 
a month to complete a circuit around the earth, Jupiter's 
moons are wonderfully brisk and lively. Nor are they 
small bodies like the satellites of Mars, for the second 
of Jupiter's satellites is quite as big as our moon, and 
the other three are very much larger. It is, however, 
true that his satellites appear insignificant when com- 
pared with Jupiter's own enormous bulk. 

The innermost of these little bodies flies right round 
in a period of one day and eighteen or nineteen hours, 
while the outermost of them takes a little more than a 
fortnight — that is, rather more than half the time that 
our moon demands for a complete revolution. Jupiter's 
satellites are too far off for us to see much with respect 
to their structure or appearance even with mighty tele- 
scopes. It is, of course, their great distance from us 
that makes them look insignificant. They would, how- 
ever, be bright enough to be seen like small stars were 
it not that, being so close to Jupiter, his overpowering 
brightness renders such faint objects in his vicinity 
invisible. 

It was by means of the satellites of Jupiter that one 
of the most beautiful scientific discoveries was made. 
As a satellite revolves round the giant planet it often 
happens that the little body enters into the shadow of 
the great planet. No sunlight will then fall upon the 
satellite, and as it has no light of its own, it disappears 
from sight until it has passed through the shadow and 
again receives sunlight on the other side. We can 
watch these eclipses with our telescopes, and there can 



220 



STAR LAND. 



be no more interesting employment for a small telescope. 
The movements of these bodies are now known so thor- 
oughly that the occurrence of the eclipses can be pre- 
dicted. The almanacs will tell when the satellite is 
calculated to disappear, and when it ought again to 
return to visibility. When astronomers first began to 
make these compulations a couple of hundred years 
ago, the little satellites gave a great deal of trouble. 
They would not keep their time. Sometimes they were 
a quarter of an hour too soon, and sometimes a quarter 
of an hour too late. At last, however, the reason for 
these irregularities was discovered, and a wonderful 
reason it was. 

Suppose there were a, number of cannons all over 

Hyde Park, and that these cannons were tired at the 
same moment by electricity. Though the sounds would 
all be produced simultaneously, yet, no matter where 

yon stood, yon would not hear them altogether; the 
noise from the cannons close at hand would reach your 
ears first, and the more distant reports would come in 
subsequently. You can calculate the distance of a flash 
of lightning if you allow a mile for every live seconds 
that elapse between the time you saw the Hash and the 
time you heard the peal of thunder which followed it. 
The light and the noise wore produced simultaneously, 
but the sound takes live seconds to pass over every mile, 
while (he light, in comparison to sound, may be said io 
move instantaneously. That sound travelled with a 
limited velocity was always obvious, but never until 
the discrepancies arose about Jupiter's satellites was it 
learned that Imht also takes time to travel. It is true 



L'UL VELOCITY OF LIGHT. 221 

that light travels much more quickly than sound — 
indeed, about a million times as fast. Light goes so 
quickly, that it would rush more than seven times 
around the earth in a single second. So far as terres- 
trial distances are concerned, the velocity of light is 
such that the time required for a journey is inappre- 
ciable. The distances, however, between one celestial 
body and another are so enormous, that even a ray of 
light, moving as quickly as it alone can move, will 
occupy a measurable time on the way. Our moon is 
comparatively so near us, that light takes little more 
than a second to cover that short distance. Eight min- 
utes are, however, required for light to travel from the 
stm to the earth : in fact, the sunbeams that now come 
into our eyes left the sun eight minutes ago. If the 
sun were to be suddenly extinguished, it would still 
seem to shine as brightly as ever in the eyes of the 
inhabitants of this earth for eight minutes longer. As 
Jupiter is five times as far from the sun as we are, it 
follows that the light from the sun to Jupiter will spend 
forty minutes on the journey, and the light from Jupiter 
to the earth will take a somewhat similar time. When 
we look at Jupiter and his moons, we do not see him as 
he is now, we see him as he was more than half an hour 
ago. but the interval will vary somewhat according to 
our different distances from the planet. Sometimes the 
light from Jupiter will reach us in as little as thirty- 
two minutes, while sometimes it will take as much as 
forty-eight — that is, the light sometimes requires for 
its journey a quarter of an hour more than is sufficient 
at other times. 



222 STAR-LAND. 

We can therefore understand that irregularity of 
Jupiter's satellites which puzzled the early astronomers. 
An eclipse sometimes appeared a quarter of an hour 
before it was expected ; because the earth was then as 
near as it could be to Jupiter, while the calculations 
had been made from observations when Jupiter was 
at his greatest distance. It was these eclipses of the 
satellites which first suggested the possibility that light 
must have a measurable speed. When this was taken 
into account, then the occasional delay of the eclipses 
was found to be satisfactorily explained. Confirmation 
flowed in from other sources, and thus the discovery of 
the velocity of light was completely established. 

Professor Barnard, when studying Jupiter in 1892 
with the splendid refractor at the Lick Observatory, 
saw a very small point of light nearer to the planet 
than the nearest of the four satellites already known. 
Further examination showed that this little object was 
indeed another satellite. Thus Jupiter has a fifth moon 
in addition to the four which have been known so long. 
This little body is so small and faint that it can only 
be discerned under the most favorable conditions by the 
most powerful telescopes. 

SATURN. 

Next outside Jupiter, on the confines of the ancient 
planetary system, revolves another grand planet, called 
Saturn. His distance from us is sometimes nearly a 
thousand millions of miles, and he requires more than 
a quarter of a century for the completion of each revo- 



SA'ITKN AND HIS KINGS. 



223 



lution. Sometimes people do not pronounce the names 
of the planets quite correctly. I have heard of a gar- 
dener who has a taste for astronomy, and sometimes 
begins to talk about the planets Juniper and Citron. 
Probably you will know what he meant to say. The 




Pig. (>s. — Saturn and the Earth compared. 

ancients had discovered Saturn to be a planet, for 
though he looked like a star, yet his movement through 
the constellations could not escape 4 their notice when 
attention was paid to the heavens. 

In the matter of size Saturn is only surpassed by 
Jupiter among the planets. He is about 600 times as 
large as the earth ; the small object, k, shown in Fig. 
68, represents our earth in its true comparative size to 
the ringed planet ; but Saturn is so far off, that even 
at his best he is never so bright as Venus, or Mars, 
or Jupiter become when they are favorably situated. 
On the globe of Saturn we can sometimes see a few 



224 STAR-LAND. 

bands, but they are faint compared with those on Jupi- 
ter. There is, however, no doubt that what we see 
upon Saturn is a dense mass of cloud. Indeed, he can 
have comparatively little solid matter inside, for this 
planet does not weigh so much as a ball of water the 
same size would do. Saturn, like Jupiter, must be 
highly heated in his interior. 

The ring, or rather series of rings, by which the planet 
is surrounded are also shown in Fig. 68 : these append- 
ages are not fastened to the globe of Saturn by any 
material bonds ; they are poised in space, without any 
support, while the globe or planet proper is placed sym- 
metrically in the interior. 

I have made a model which shows Saturn with his 
rings, but it is necessary for me to fasten the rings by 
little pieces of wire to the globe, for there is no mechan- 
ical means by which the rings of the model could be 
poised without support, as they are around the planet. 
If we throw the beam of the electric lamp on the little 
planet, we see the shadow which the planet casts on its 
ring. Similar shadows can be observed in the actual 
Saturn of the sky, and this is a proof that the planet 
does not shine by its own light, but by the light of the 
sun which falls upon it. Here again we illustrate the 
wide difference between a planet and a star, for were 
our sun to be put out, Saturn and all the other planets 
in the sky would vanish from sight, while the stars 
would, of course, twinkle on as before. There are three 
rings round Saturn ; they all lie in the same plane, and 
they are so thin, that when turned edgewise towards us 
the whole system almost disappears, except in very 



HOW BRIDGES STAND. 225 

powerful telescopes. The outer and the inner bright 
rings are divided by a dark line, which can be traced 
entirely round. At the inner edge of the inner ring 
begins that strange structure called the crape ring, 
which extends halfway towards the globe of the planet. 
The most remarkable point about the crape ring is its 
semi-transparency, for we can sometimes see the globe 
of the planet through this strange curtain. The crape 
ring can only be observed with a powerful telescope. 
The other two rings are within the power of very mod- 
erate instruments. 

THE NATURE OF THE RINGS. 

For the explanation of the nature of Saturn's rings 
we are indebted to the calculations of mathematicians. 
You might have thought, perhaps, that nothing would 
be simpler than to suppose the rings were stiff plates 
made from solid material. But the question cannot be 
thus settled. We know that the ring could not bear 
the strain of the planet's attraction upon it if it were a 
solid body. I may illustrate the argument by familiar 
facts about bridges. Where the span is but a small one, 
as, for instance, when a road has to cross a railway, a 
canal, or a river, the arch is, of course, the proper kind 
of structure. There is, for example, a specially beauti- 
ful arch over the river Dee at Chester. But if the 
bridge be longer than this, masonry arches are not 
suitable. Where a considerable span has to be crossed, 
as at the Menai Straits, or a gigantic one, as at the 
Firth of Forth, then arches have to be abandoned, and 



226 STAR-LAND. 

iron bridges of a totally different construction have to 
be employed. Arches cannot be used beyond a limited 
span, because the strain upon the materials becomes too 
great for their powers of resistance to withstand. Each 
of the stones in an arch is squeezed by intense pressure, 
and there is a limit beyond which even the stoutest 
stones cannot be relied upon. As soon, therefore, as 
the span of the arch is so great that the stones it con- 
tains are squeezed as far as is compatible with safety, 
then the limit of size for that form of arch has been 
reached. 

Suppose that you stood on Saturn at his equator, 
and looked up at the mighty ring which would stretch 
edgewise across your sky. It would rise up from the 
horizon on one side, and, passing over your head, would 
slope down to the horizon on the other. You would, 
in fact, be under an arch of which the span was about 
100,000 miles. Owing to the attraction of Saturn, 
every part of that structure would be pulled forcibly 
towards his surface, and thus the materials of the arch, 
if it were a solid body, would be compressed with ter- 
rific force. 

It does not really signify that the arch I am now 
speaking of is half of a ring the other half of which is 
below the globe of the planet. That is only a difference 
with respect to the support of two ends of the arch, 
and does not affect the question as to the pressure upon 
its materials ; nor does the fact that the ring is revolv- 
ing remove the difficulty, though it undoubtedly lessens 
it. We know no solid substance which could endure 
the pressure. Even the toughest steel that ever was 



AN OLD FABLE. 227 

made would bend up like dough under such conditions. 
We cannot, therefore, account for Saturn's ring by sup- 
posing it to be a solid, for no solid would be strong 
enough. 

Do you not remember the old fable of the oak tree 
and the pliant reed — how when the storm was about 
to arise the oak laughed at the poor reed, and said it 
would never be able to withstand the blasts? But 
matters did not so turn out. The mighty oak, which 
would not yield to the storm, was blown down, while 
the slender reed bent to the wind and suffered no 
injury. This gives us a hint as to the true constitu- 
tion of Saturn's ring ; it is not a solid body, trying to 
resist by mere strength ; it is rather to be explained as 
an excessively pliant structure. Indeed, I ought not 
to call it a structure at all ; it is rather a multitude of 
small bodies not in the least attached together. I do 
not know what the size of these bodies may be. For 
anything we can tell, they may be no larger than the 
pebbles you find on a gravel walk. 

Let us see how we could encircle our earth with 
rings like those which surround Saturn. I shall ask 
you to be provided with a sufficiently large number of 
pebbles, and you must also imagine that I have the 
means of ascending high up into space, halfway from 
here to the moon. Suppose I went up there and simply 
dropped the pebble, of course, it would tumble straight 
down to the earth again. If, however, I threw it out 
with proper speed and in the proper direction, I could 
start it off like a little moon, and it would go on round 
and round our earth in a circle. I mention a pebble, 



228 STAR-LAND. 

but really it is little matter what the size of the object 
may be — it may be as small as a grain of shot or as big 
as a cannon-ball. Now take another pebble. Cast it 
also in a somewhat similar path, taking care, however, 
that the planes of the two orbits shall be the same. 
Each of these little bodies shall pursue its journey 
without interference from the other. Then proceed in 
the same way with a third, a fourth, with thousands 
and millions and billions of pebbles, until at last the 
small bodies will become so numerous that they almost 
fill a large part of the plane with a continuous shoal. 
Each little object, guided entirely by the earth's attrac- 
tion, will pursue its path with undeviating regularity. 
Its neighbors will not interfere with it, nor will it inter- 
fere with them. Let us circumscribe the limits of our 
flat shoal of moonlets. We first take away all those 
that lie outside a certain large circle; then we shall 
clear away sufficient to make a vacant space between 
the outer ring and the inner ring, and thus the two 
conspicuous rings have been made ; at the inside of the 
inner ring we shall take out numbers of pebbles here 
and there, so as to make this part much less dense 
than the outer portions, and thus produce a semi-trans- 
parent crape ring ; then we shall clear away those that 
come too close to the planet, and form a neat inner 
boundary. 

Could we then view our handiwork from the stand- 
point of another planet, what appearance would our 
earth present? The several pebbles, though individ- 
ually so small, would yet, by their countless numbers, 
reflect the sun's light so as to produce the appearance 



MOONLETS. 229 

of a continuous sheet. Thus we should find a large 
bright outer ring surrounding the earth, separated by a 
dark interval from the inner ring, and at the margin 
of the inner ring the pebbles would be so much more 
sparsely distributed that we should be able to see 
through them to some extent. That beautiful system 
of rings which Saturn displays is undoubtedly of a 
similar character to the hypothetical system which I 
have endeavored to describe. No other explanation 
will account for the facts, especially for the semi-trans- 
parency of the crape ring. The separate bodies from 
which Saturn's rings are constituted seem, however, 
so small that we are not able to see them individually. 
There are some other fine lines running round the 
rings beside the great division, and these can also be 
explained by the theory I have stated. 

Saturn has other claims on our attention besides those 
of its rings. It has an elaborate retinue of satellites — 
no fewer, indeed, than nine ; but some of them are very 
faint objects, and not by any means so interesting as 
the system by which Jupiter is attended. The ninth 
of these was discovered quite recently by Professor 
W. H. Pickering, of Harvard College Observatory. 
This little moon, for which the name " Phoebe " has 
been suggested, is further from the planet than any of 
the others. It is a minute object shining as a star of 
the 15th or 16th magnitude, and moves around the 
planet in a period of about sixteen months. 

Saturn was the last and outermost of the planets 
with which the ancients were acquainted. Its path 
lay on the frontiers of the then known solar system, 



230 STAK-LAND. 

and the magnificence of the planet itself, with its at- 
tendant luminaries and its marvellous rings, rendered 
it worthy indeed of a position so dignified. These five 
planets — namely, Mercury, Venus, Mars, Jupiter, and 
Saturn — made up with the sun and the moon the seven 
" planets " of the ancients. They were supposed to com- 
plete the solar system, and, furthermore, the existence 
of other members was thought to be impossible. In 
modern times it has been discovered that there are yet 
two more planets. I do not now refer to those little 
bodies which run about in scores between Mars and 
Jupiter. I mean two grand first-class planets, far 
bigger than our earth. One of them is Uranus, which 
revolves far outside Saturn, and the other is Neptune, 
which is much further still, and whose mighty orbit 
includes the whole planetary system in its circuit. To 
complete its journey round the sun not less than 165 
years is required. 

WILLIAM HEKSCHEL. 

I have to begin the account of this discovery by tell- 
ing you a little story. In the middle of the last century 
there lived at Hanover a teacher of music whose name 
was Isaac Herschel. He had a family of ten children, 
and he did the best for them that his scanty means 
would permit. Of his children William was the fourth, 
and he inherited his father's talents for music, as did 
most of his brothers and sisters. He was a bright, 
clever boy at school, and he made such good progress 
in his music that by the time he was fourteen years old 



HEESCHEL AS A MUSICIAN. 231 

he was able to play in the military band of the Hano- 
verian Guards. War broke out between France and 
England, and as Hanover was then under the English 
crown, the French invaded it, and a battle was fought 
in which the poor Hanoverian Guards suffered very 
terribly. Young Herschel spent the night after the 
battle in a ditch, and he came to the conclusion that he 
did not like fighting, though he was only a member of 
the band, and he resolved to change his profession. 
That was not so easy to do just then, for even a bands- 
man cannot leave the service in war time at his own 
free will. William Herschel, however, showed all 
through his life that he was not the man to be baffled 
by difficulties. I do not know whether he asked for 
leave, but at all events he took it. He deserted, in 
fact, and his friends succeeded in sending him away to 
England. 

He was nineteen years old when he commenced to 
look for a career over here, and certainly he found his 
prospects in the musical profession very discouraging. 
Herschel was, however, very industrious ; and at last he 
succeeded in getting appointed as organist of the Octa- 
gon Chapel at Bath. He gradually became famous for 
his musical skill, and had numbers of pupils. He used 
also to conduct concerts and oratorios, and was well 
known in this way over the West of England. Busy 
as Herschel was with his profession, he still retained 
his love of reading and study. Every moment he could 
spare from his duties he devoted to his books. It was 
natural that a musician should specially desire to study 
the theory of music, and to understand it properly you 



232 STAR-LAND. 

should know Euclid and algebra, and, indeed, higher 
branches of mathematics as well. Herschel did not 
know these things at first ; he had not the means of 
learning them when he was a boy, so he worked very 
hard after he became a man. And he studied with 
such success that he made fair progress in mathematics, 
and then it appeared to him that it would be interesting 
to learn something about astronomy. After he had 
begun to read about the stars, he thought he would 
like to see them, and so he borrowed a telescope. It 
was only a little instrument, but it delighted him so 
much that he said he must have one for himself. So he 
wrote to London to make inquiries. 

Telescopes were much dearer in those days than they 
are now, and Herschel could not give the price that the 
opticians demanded. Here again his invincible deter- 
mination came to his aid. What was there to prevent 
him from making a telescope ? he asked himself ; and 
forthwith he began the attempt. You will think it 
strange, perhaps, that a music-teacher who had no 
special training as a mechanic should at once commence 
so delicate and difficult a task ; but it is not really so 
hard to make a telescope as might be imagined. The 
amateur cannot make such a pretty-looking instrument 
as he is able to buy at the shops — the tubes will not be 
so beautifully polished and the finish will be such as a 
trained workman would be ashamed of — but the essen- 
tial part of a telescope is comparatively easy to make ; 
at least, I should say of a reflecting telescope, which is 
the kind Herschel attempted to make, and succeeded in 
making. You must know that there are two kinds of 



HERSCHEL AND HIS TELESCOPE. 233 

telescopes. The commoner one with, which you are more 
familiar is called the refracting telescope, and it has 
glass lenses. It was an instrument constructed on this 
principle that we spoke of in a former lecture (p. 97). 
The reflecting telescope depends for its power upon a 
bright mirror at the lower end, and when using this 
instrument you look at the reflection of the stars in the 
mirror. It was a reflector like this that Herschel began 
to construct, and he engaged in the task with enthu- 
siasm. His sister Caroline had come to live with him, 
and she used to help him at his work. So much in 
earnest was he that he used to rush into his workshop 
directly he came home from a concert, and without tak- 
ing off his best clothes he would plunge into the grind- 
ing and polishing of his mirrors. His sister tried to 
keep the house as tidy as possible, but Herschel put up 
a carpenter's shop in the drawing-room, and turning- 
lathes in the best bedroom. At last he succeeded. He 
made a mirror of the right shape, and found that it 
exhibited the stars properly. It was not a looking- 
glass in the ordinary sense, with glass on one side and 
quicksilver on the other. The mirror that Herschel 
constructed was entirely of metal. It consisted of a 
mixture of two parts of copper with one of tin. 

The copper has first to be melted in a furnace, for 
the metal must be above a red heat before it will begin 
to run. Then the tin has to be carefully added, and 
the casting of the mirror is effected by pouring the 
molten metal into a flat mould. Thus the rough mirror 
is obtained, which in Herschel's earlier telescopes seems 
to have been about six or seven inches in diameter, and 



234 



STAR-LAND. 



nearly an inch thick. Though copper is such a tough 
substance, and though tin is also tough, yet when melted 
together to make speculum metal, as this alloy is called, 
they produce an exceedingly hard and brittle material. 
When we remember that we could never break a copper 
penny piece by throwing it down on the flags, it may 
seem strange that the " speculum metal" should be so 
exceedingly brittle. A piece the size of a penny would 




Fig. (>9. — The Mirror. 



be more brittle than a bit of glass of the same dimen- 
sions, and when the speculum is cast, unless it is cooled 
very carefully, it will fly into pieces. Herein lay one 
of the difficulties that Herschel encountered. Speculum 
metal must be put into an oven as soon as the casting 
has become solid, and then the heat is gradually allowed 
to abate. When the speculum has been at last obtained, 
next follows the labor of giving it the true figure and 
polish. It is not only more fragile than glass, but it is 
also quite as hard, and therefore the grinding is a tedi- 
ous operation. First the surface has to be ground with 
coarse sand, and then with emery, which is gradually 
made finer and finer until the true figure has been 
given (Fig. 69). The mirror is then somewhat basin- 
shaped, but the depression is very slight. For example, 
in a mirror six inches across the depression at the centre 



HOW HE MADE IT. 



235 




would perhaps be not more than the twentieth of an 
inch. Small though this depression is, yet it has to be 
made with exactness. In fact, if it were wrong at any 
point by so much as the tenth of the thickness of this 
sheet of paper, the telescope would not perform accu- 
rately. The tool that is used in grinding is made of 
cast iron, and has been turned in a lathe to the right 
shape. It is divided into squares 
in the manner shown in Fig. 70. 
After the grinding comes the 
polishing, and this is effected with 
a tool like the grinder in shape. 
This has to be covered over with 
little squares of pitch, so that when 
warmed and put down on the 
mirror it is soft enough to receive 
the right shape. Some rouge 

and w r ater is spread over the mirror, and the polisher is 
worked backward and forward with the hand until a 
brilliant surface is obtained. 

When the amateur astronomer has completed this 
part of the task, all the great difficulties about his tele- 
scope are conquered. The tube may be made of wood, 
and, indeed, a square tube will do just as well as a 
round one. He must also provide for the top of the 
tube a small mirror, which has to be perfectly flat. The 
preparation of this requires much care, because it is not 
so easy as one might suppose to obtain an accurately 
flat surface. One way of doing this is to get three 
pieces, and grind each two of them together until every 
pair will touch all over : then they will certainly all be 



Fig. 70. — The Grinding 
Tool. 



236 STAR-LAND. 

flat. One more part you want, and that is an eyepiece. 
This presents no difficulty. A single glass lens can be 
made to answer and your telescope is complete. 

THE DISCOVERY OF URANUS. 

It was in the year 1774 that Herschel first had a 
view of the heavens through the telescope he had him- 
self constructed. During the early part of his career 
he does not seem to have made any important dis- 
coveries. He was gradually preparing himself for the 
great achievement by which his name became famous. 

It was on the 13th of March, 1781, that the organist 
of the Octagon Chapel at Bath turned his telescope 
on the constellation of the Twins, and began to look at 
one star after another. You must know that a star 
merely looks like a little point in a telescope ; even the 
greatest instrument will only make a star look brighter, 
and will never show it with a perceptible disk. In look- 
ing over the stars that night, Herschel's attention was 
arrested by one object that did look larger when mag- 
nified, and therefore was not a star. The only other 
objects which would behave in this way were the 
planets, or possibly a comet. Indeed, at first Herschel 
imagined that what he saw must be a comet. It could 
hardly have occurred to him that he was to have such 
good fortune as to discover a new planet. The five 
great planets had been known from all antiquity. Was 
it reasonable to suppose that there could be yet another 
that had never been perceived? Fortunately, there 
was a test available. A star remains in the same place 



HIS DISCOVERY. 237 

from night to night and from year to year; while a 
planet, as we have already had occasion to mention, is 
a body which is wandering about. The movements of 
a planet are, however, not at all like those of a comet. 
To decide on the nature of Herschel's newly discovered 
body, it was sufficient to observe the character of its 
motion. A few nights sufficed to do this. The posi- 
tion of the body was carefully marked relatively to the 
neighboring stars, and it was soon shown that it was a 
planet. 

Here, then, a great discovery was made. A new 
planet, now called Uranus, was added to our system. 
It would be nothing to discover a new star. You might 
as well talk of discovering a new grain of sand on the 
seashore. The stars are in untold myriads. They 
are so far off that they have no relation whatever to 
our system, which is presided over by the sun. But 
by the detection of a new planet, revolving far outside 
Saturn, Herschel showed that a new and most interest- 
ing member had to be added to the five old planets 
which have been known from the earliest records of 
history. 

It may well be imagined that a discovery so startling 
as this excited astonishment throughout the scientific 
world. " Who is this Bath organist ? " everybody asked. 
Accounts of him and his discoveries appeared in the 
papers. His fellow-citizens were not so familiar with 
the name as we are, happily, now; and the spelling 
of the unusual name showed many varieties. When 
George III. heard of Herschel's great achievement, he 
directed the astronomer to be summoned to Windsor, 



238 STAR-LAND. 

that the King might receive an account of the wonderful 
discovery from the lips of the discoverer himself. Her- 
schel of course obeyed, and he brought with him his 
famous telescope, and also a map of the whole solar 
system, to show to the King. No doubt he thought 
that his Majesty had probably not paid much attention 
to astronomy. Herschel was, therefore, prepared to 
explain to the King what it would be necessary for him 
to know before he could fully appreciate the magnitude 
of the discovery. 

You will remember that Herschel while still a boy 
had deserted from the army, many years previously. 
It appears that the King had learned this fact in some 
way, so that when Herschel was ushered into his pres- 
ence his Majesty said that before the great astronomer 
could discuss science there was a little matter of busi- 
ness that must be disposed of. The King accordingly 
handed Herschel a paper, in which he was, I dare say, 
greatly surprised to find a pardon to the deserter written 
out by the King himself. 

Then Herschel unfolded his wonderful discovery, 
which the King thoroughly appreciated, and in the 
evening the telescope was set up in the gardens, and 
the glories of the heavens were displayed. Herschel 
made a most favorable impression on his Majesty, and 
when the King told the ladies of the Castle next day 
of all that Herschel had shown him, their astronomical 
ardor was also aroused, and they asked to see through 
the marvellous tube. Of course Herschel was ready to 
comply, and the telescope was accordingly carried to 
the windows of the Queen's apartments at Windsor, 



HOW THE COURT LADIES SAW SATURN. 239 

which would have commanded a fine view if the clouds 
had not been in the way, which they unfortunately 
were. Even for royalty the clouds would not disperse, 
so what was to be done ? Herschel was equal to the 
occasion. He specially wanted to exhibit Saturn, for it 
is one of the most beautiful objects in the sky, and will 
fascinate any intelligent beholder. No astronomers 
would have been able to see Saturn through the clouds, 
but Herschel did not disappoint his visitors ; he directed 
the instrument, not to the sky (nothing was there to be 
seen) ; he turned it towards a distant garden wall. Now 
what would you expect to see by looking through a 
telescope at a garden wall — bricks, perhaps, or ivy ? 
What these ladies saw w r as a beautiful image of Saturn, 
his globe in the centre and his rings all complete, form- 
ing so true a resemblance to the planet that even an 
experienced astronomer might have been deceived. In 
the afternoon Herschel had seen that the clouds were 
thick, and that there would be little probability of using 
the telescope properly. Accordingly he cut out a little 
image of Saturn, illuminated it by lamps, and set it up 
at a suitable distance on a garden wall. 

Herschel's visit to Windsor was productive of impor- 
tant consequences. The King said it was a pity that 
so great an astronomer should devote himself to music, 
and that it would be far better for him to give up that 
profession and come and live at Windsor. His Majesty 
promised that he would pay him a salary, and he also 
undertook to provide the cost of erecting great tele- 
scopes. His faithful sister Caroline came with him as 
his assistant, and also received some bounty from the 



l!40 STAR-LAND. 

King. From that moment Herschel renounced all his 
musical business, and devoted himself to his great life- 
task of observing the heavens. 

He built telescopes of proportions far exceeding those 
that had ever been then thought of. He used to stand 
at night in the open air from dusk to dawn gazing down 
the tube of his mighty reflector, watching the stars and 
other objects in the heavens as they moved past. He 
would dictate what he saw to Caroline, who sat near 
him. It was her business to write down his notes and 
to record the position of the objects which he was 
describing. Sometimes, she tells us, the cold was so 
great that the ink used to freeze in her pen when she 
was at this work. Until he became a very old man, 
Herschel devoted himself to his astronomical labors. 
His discoveries are to be counted by thousands, though 
not one of them was so striking or so important as 
the detection of the new planet which first brought 
him fame. 

The question of a name for the addition to the sun's 
family had, of course, to be settled. Herschel had surely 
a right to be heard at the christening, and as a com- 
pliment to his Majesty he named the stranger the 
Georgium Sidus. So, indeed, for a brief while, the 
planet was actually styled. The Continental astrono- 
mers, however, would not accept this designation ; all 
the other planets were named after ancient divinities, 
and it was thought that the King of England would 
seem oddly associated with Jupiter and Saturn ; per- 
haps also they considered that the British dominions, 
on which the sun never sets, were already quite large 



THE PLANET URANUS. 241 

enough, without further extension to the celestial 
regions. Accordingly a consultation was held, the 
result of which was that George III. was deprived 
of his planetary honors, and the body was given the 
name of Uranus, which, by universal consent, it now 
bears. 

The planet Uranus lies just on the verge of visibility 
with the unaided eye. It can sometimes be glimpsed 
like a faint star, and, of course, with a telescope it is 
readily perceived. Many generations of astronomers 
before Herschel's time had been observing the heavens, 
making maps of the stars, and compiling great cata- 
logues in which the places of the stars were accurately 
put down. It often happened that Uranus came under 
their notice, but it never occurred to them that what 
seemed so like a star was really a planet. I have, no 
doubt, said that Uranus looked unlike a star when 
Herschel examined it; but then that was because 
Herschel was a particularly skilful astronomer. To 
an observer of a more ordinary type Uranus would 
not present any very remarkable appearance, and would 
be passed over merely as a small star. In fact, the 
planet was thus observed not once or twice, but no 
fewer than seventeen times, before the acute eye of 
Herschel perceived its true character. On many pre- 
vious occasions the planet had been noted as a star by 
astronomers who are in every way entitled to our 
respect. It required a Herschel, determined to see 
everything in the very best manner, to grasp the dis- 
covery which eluded so many others. 

When Uranus was observed on these former occasions 



242 STAR-LAND. 

and mistaken for a star, its place had been carefully put 
down. These records are at present of the utmost use, 
because they show the past history of the planet ; and 
they appear all the more valuable when we remember 
that Uranus requires no less than eighty-four years to 
accomplish a single revolution around the sun. Thus, 
since the planet was discovered in 1781, it had com- 
pleted one revolution by 1865, and is now (1899) about 
one-third of the way around another. The earlier 
observations extend backwards almost 200 years, so 
that altogether we have more or less information about 
the movements of the planet during the completion of 
two circuits and a half. 

Uranus is a great deal bigger than the earth, as you 
will see in the view of the comparative sizes of the 
planets (Fig. 47). It appears to be of a bluish hue, but 
we cannot tell whether it turns round on its axis, or 
rather, I should say, we are not able to see whether it 
turns round on its axis ; for we can hardly doubt that 
it does so. 

Notwithstanding that Uranus is at so great a distance 
from the earth, we have been able to put this planet, 
no less than the nearer ones, in the weighing scales, and 
we assert with confidence that Uranus is fifteen times 
as heavy as our earth. We are indebted to the satellites 
for this information. 

THE SATELLITES OF URANUS. 

You must use a very good telescope to see the 
satellites of Uranus. They are four in number, bear- 



URANUS' SATELLITES. 243 

ing the names of Ariel, Umbriel, Titania, and Oberon. 
The innermost of these, Ariel, completes a journey 
round the planet in two days and a half ; Oberon, the 
most distant, requires thirteen days and a half. A 
planet is always tending to pull its satellite down, and 
the satellite is kept from falling by the speed with 
which it revolves. The heavier the planet, the faster 
must its satellites go round. Thus, to take an illustra- 
tion from our own moon, we know that, if the earth 
were to be made four times heavier than it is, the moon 
would have to spin round twice as fast as it does, in 
order to remain in the same orbit. The speed with 
which the satellites of Uranus revolve accordingly 
affords a measure, of the mass of the planet. Were 
Uranus heavier than he is, his satellites would revolve 
more quickly than they do ; were he lighter, the 
satellites would take a longer period to go round. 

Uranus also seems to be greatly swollen by clouds, in 
the same manner as are both Jupiter and Saturn ; in 
fact, if our earth was as big as Uranus, it would weigh 
four or five times as much as Uranus does. Hence we 
are certain that Uranus must consist of materials less 
dense on the whole than are those of which our earth is 
made. 

There is another singular circumstance connected 
with the moons of Uranus. I have told you how every 
body revolving round another by gravitation will de- 
scribe an ellipse ; but, of course, there are many different 
kinds of this curve, and some may be nearly circles. 
There is nothing whatever to prevent a satellite from 
revolving around its primary in an exact circle if it be 



244 STAR-LAND. 

started properly ; that is, in the right direction and 
with the right speed. All the four satellites of this 
planet seem to revolve in circles so perfect that we can 
make an accurate picture of this system with a pair of 
compasses. It is further to be noticed that the four 
circles seem to lie exactly in the same plane. The 
orbits of the other great planets and of their satellites 
lie in planes inclined at angles of less than 35° to the 
ecliptic, the plane in which the earth moves. Here 
again the satellites of Uranus are exceptional. The 
plane in which they are contained stands up almost 
squarely to the plane in which the motion of the planet 
is performed. The moons of Uranus seem to have got 
a twist, from some accidental circumstance for which 
we are not able to account. 

THE DISCOVERY OF NEPTUNE. 

The boundaries of the solar system had been much 
extended by the discovery of Uranus, but they were 
destined to receive still further enlargement by the 
detection of another vast planet, revolving far outside 
Uranus, the orbit of which forms, according to our pres- 
ent knowledge, the outline of the planetary system. 

I have here to describe one of the greatest discov- 
eries that have ever been made. It is not the magnifi- 
cence of the outermost planet itself that I refer to, 
though, indeed, it is bigger than Uranus. I am rather 
thinking of the way in which the discovery was made. 
I do not mean any disrespect to Herschel when I say 
that the discovery of Uranus was chiefly a stroke of 



DISCOVERY OF NEPTUNE. 245 

good fortune ; but I may be permitted to describe it in 
this manner by way of emphasizing as strongly as I can 
how utterly different was the train of ideas which led 
to the discovery of Neptune. Herschel merely looked 
at one star after another till suddenly he dropped on 
the planet, having beforehand not the slightest notion 
that any such planet was likely to exist. But Neptune 
was shown to exist before it was ever seen, and, in fact, 
the man that first saw the planet, and knew it to be a 
planet, was not the discoverer. This is rather a diffi- 
cult subject ; and it would take you years of hard study 
to be able to understand the train of reasoning by which 
Neptune was found. I shall, however, make an attempt 
to explain this matter sufficiently to give at least some 
idea of the kind of problem that had to be solved. 

You will remember that law of Kepler which tells us 
that every planet moves round the sun in an ellipse. 
If the planet be uninterfered with in any way and 
guided only by the attraction of the sun, it will forever 
continue to describe precisely the same ellipse without 
the slightest alteration. It was ascertained that the 
path which Uranus followed was not always regular. 
The early observations of the planet, when it was mis- 
taken for a star, have here been of the utmost service. 
They have indicated the ellipse which Uranus described 
the last time it went round, and our modern observa- 
tions have taught us the path which the planet is at 
present describing. These two ellipses are slightly dif- 
ferent, and the consequence is that, supposing we take 
the observations of Uranus made 100 years ago, and 
calculate from them where Uranus ought to be now, we 



246 STAR-LAND. 

find that the planet is a little astray. Astronomers are 
not accustomed to be wrong in such calculations, and 
when discrepancies arise, the first thing to be done is to 
see what has caused them. It is certain that the posi- 
tion in which Uranus is found this very night, for 
example, is not what it would have been had the sun 
alone been guiding the planet. Perhaps you will think 
that it is impossible for reliable computations to be 
made about such matters ; but I assure you they can, 
and the very fact that the motion of Uranus appeared 
to be irregular made it interesting to try and find out 
the cause of the disturbance. 

I have already explained, when speaking about Mars 
(p. 187), that there is an attraction between every two 
bodies, but in the group of planets to which the earth 
belongs the sun's attraction is so much stronger than 
any other force that all the movements are guided 
mainly by it. Nevertheless it is true that not only does 
the sun pull our earth and all the other planets as well, 
but all the planets, including the earth, are pulling one 
another. In fact, there is an incessant struggle going 
on in the family party. Fortunately the sun is so 
much more powerful than any other member, that he 
keeps them all pretty well in order ; and unless you 
look very carefully you will not see the effects of the 
little struggles that are going on between every pair of 
the system. Our earth itself is pulled and swayed to 
and fro by the actions of its brothers and sisters. It is 
dragged perhaps a thousand or two thousand miles this 
way by Jupiter, or it gets a good tug in the other 
direction by Venus. Mars and Saturn also do their 



WHO WAS PULLING URANUS? 247 

little best to force the earth away from its strict path. 
However, our earth does not suffer much from these 
irregularities. It pursues its route fairly enough, just 
as a coach from London to Brighton will get safely to 
its destination notwithstanding the fact that it has to 
swerve a little from its path whenever it meets other 
vehicles on the way, or when the coachman wishes to 
avoid a piece of the road on which stones have been 
freshly laid down. 

The track followed by Uranus was found to be some- 
what irregular, like that of every other planet. Jupiter 
gave it a pull, and so did Saturn, and at first it was 
thought that the irregularities which were perceived 
could be explained by the action of these planets, so 
big and so well known. Here is a question for calcula- 
tion ; it involves a very long and a very hard piece of 
work, but it is possible to estimate how far each of the 
other planets is capable of dragging Uranus from its 
path. Is it not remarkable that by working out long 
calculations we should be able to find Avhat one planet 
hundreds of millions of miles away was able to do to 
another planet still further off, and not only for to-day 
or yesterday, but for past time extending over more 
than a century? If, however, you will listen to me a 
little longer, I think I shall give you a proof that these 
sums could be worked out correctly. 

When the calculations had been made which showed 
how much the known planets could disturb Uranus, it 
was found that there were still some deviations of the 
planet that remained unexplained. They were not large ; 
they only amounted to showing that the body was just 



248 STAR-LAND. 

a little astray from the spot where the calculations 
indicated it should be. The rest of astronomy was so 
perfect, and the law of attraction prevailed so univer- 
sally, that it was thought the law of attraction must 
provide some way of explaining the behavior of Uranus. 
He could not have left his track of his own accord ; 
therefore there must be some agency at work upon him 
of which we did not know. What could this unknown 
source of disturbance be ? Every such trouble had 
hitherto been found to be a consequence of the attrac- 
tion of gravitation ; therefore there must be some 
unknown body pulling at Uranus which no one had 
ever seen. Where could it be? How was it to be 
discovered? Such were the questions that were asked, 
and they were answered in a most satisfactory manner. 
First of all, what sort of body could it be that was 
pulling Uranus ? It is obvious that none of the stars 
would be competent to produce so great an effect ; 
they are all so far off that they have nothing whatever 
to say to any of the domestic matters in our little solar 
system, which is simply a group by itself. It would be 
more reasonable to suppose that there must be yet 
another planet which nobody had ever recognized, but 
which affected Uranus so as to account for his truant 
behavior. To begin to search for this planet with tele- 
scopes without some guidance would be futile ; in fact, 
astronomers had been scanning the heavens for planets 
for nearly fifty years, and though several had been dis- 
covered, they all belonged to the zone of little planets, 
and none of them were big enough to pull Uranus about 
appreciably. Of course, if all the stars could be blotted 



ADAMS AND LEVERRIEK. 249 

out of the sky, so that nothing but planets were left, 
then, by sweeping the telescope over the heavens, every 
planet that exists might be speedily found. The diffi- 
culty is that the planets, which are either small or very 
distant, look so like the stars that it is impossible to 
recognize them among the millions of glittering points 
in the sky. It was, however, hoped that the unknown 
planet would be large enough to be visible in the tele- 
scope, if only we knew exactly where to point it. 

Two illustrious astronomers, Adams of Cambridge, 
and Leverrier of Paris, both separately undertook an 
astonishing piece of calculation. They tried to find 
out the position of the unknown planet from the mere 
fact that it deranged Uranus in a particular way. I 
dare say many of those who are reading this book have 
learned simple equations in algebra, and they have 
worked such questions as to find the length of a pole, 
half of which is in mud, a quarter in water, and ten 
feet above the water. Those who know this much can 
perhaps realize the problem that had to be solved in 
trying to discover the unknown planet. So difficult a 
question as this had to be solved in a way that your 
masters would hardly allow you to use when working 
your sums in algebra. I do not think they would let 
you make a series of guesses. Let us try 20 feet, for 
instance, as the length of the pole ; that will make 10 
feet in the mud, 5 feet in the water, and 5 feet outside. 
This will not do ; it is not enough ; Ave must try again ; 
and after another guess or two, we see that a pole 40 
feet long will exactly answer. We do not use this 
method of guessing in algebra, because solving the 



250 STAR-LAND. 

simple equation is a much better method. Adams and 
Leverrier found that to discover the unknown planet 
was a question so very difficult, that they were obliged 
to use a sort of guessing, but very intelligent guessing, 
I need hardly assure you. They proceeded in this way 
(Fig. 71). They would draw a circle outside the path 




Fig. 71. — Orbits of Uranus and Neptune. 

of Uranus, and then suppose that a planet was revolv- 
ing in that circle. Its effect upon Uranus would then 
be calculated, and it would be found whether the ob- 
served irregularities could be in this manner accounted 
for. The first planet they tried was not the right one ; 
then they began again with another, until at last, after 
many trials and much very hard work, they saw that 
there might be a planet in a particular path far outside 
Uranus, such that if this planet were of the right 
weight and moving with the right speed, then it would 
pull Uranus exactly in the way that astronomers had 
observed it to be pulled. They found at last that there 



A PLANET ON PAPEK. 251 

could be little doubt about the matter ; for this unknown 
body would account for all the facts. Then, indeed, 
they had solved their equation ; they had found the 
unknown. 

The two great astronomers had thus discovered a 
planet, but as yet it was only a planet on paper. Those 
who could judge of the subject had no doubt that the 
planet was really in the sky ; but just as you like to 
prove that you have found the correct answer to your 
sum, so people were naturally anxious to prove the truth 
of this wonderful sum that Adams and Leverrier had 
worked out. This was to be done by actually seeing 
the planet of which the astronomers had asserted the 
existence. Leverrier calculated that the new planet in 
a certain night would be in a particular position on the 
sky. Accordingly he wrote to Dr. Galle, of the observ- 
atory at Berlin, requesting him on the evening in ques- 
tion to point his telescope to the very spot indicated, 
and there he would see a planet which human eyes had 
never before beheld. Of course, Dr. Galle was only 
too delighted to undertake so marvellous a commission. 
The evening was fine ; the telescope was opened ; it 
was directed towards the heavens ; and there, in the 
very spot which the calculations of Leverrier had indi- 
cated, shone the beautiful little planet. At Cambridge 
arrangements had also been made to search for the new 
member of the solar system, in accordance with Pro- 
fessor Adams' calculations. There also the planet that 
had given all this trouble to Uranus was brought to 
light. At first it looked like a star, as all such planets 
do ; but that it was not a star was speedily proved, by 



252 STAR-LAND. 

the two tests which are sure indications of a planet. 
First the body was so moving that its position with 
respect to the adjacent stars was constantly changing. 
Then, when a strong magnifying power was placed on 
the telescope, the little object was seen, not to be a 
mere starlike point, but to expand into the little disk 
which shows us we are not looking at a distant sun, but 
at a world like our own. 

Was not this truly a great discovery ? Have we not 
shown you how entitled the calculations of astronomers 
are to our respect, when we find that they actually dis- 
covered the existence of a majestic planet before the 
telescope had revealed it ? See also the greatly increased 
interest that belongs to Herschel's discovery of Uranus. 
We can hardly imagine anything that would have given 
more gratification to this old astronomer than to think 
that his Uranus should have given rise to a discovery 
even more splendid than his own.. He died, however, 
more than twenty years before this achievement. 

The authorities who decide on such matters christened 
the new planet Neptune ; and this body wanders round 
on the outskirts of our solar system, requiring for each 
journey a period of no less than 165 years. The circle 
thus described has a radius thirty times as great as that 
of the earth's track. 

Neptune is altogether invisible to the unaided eye, 
but it is sufficiently bright to have been . occasionally 
recorded as a star. Indeed, nearly fifty years before it 
was actually discovered to be a planet it had been 
included by the astronomer Lalande in a list of stars he 
was observing. A curious circumstance was afterwards 



A NARROW ESCAPE. 253 

brought to light. When reference was made to the 
books in which Lalande's observations were written, 
it was found that he had observed this object twice, 
namely, on May 8 and May 10, 1785. Of course, if 
the object had indeed been a star its position on the 
two days would have been the same, but being a planet 
it had moved. When Lalande, on looking over his 
papers, saw that the places of this supposed star were 
different on the two nights, he concluded that he must 
have made a mistake on the first night, and accordingly 
treated the object as if the place on the 10th was the 
right one. Just think how narrowly Lalande missed 
making a discovery ! Unhappily for his renown, he 
took it for granted that one or both of his observations 
were erroneous, and so they must have been if the 
object had been a star. But they were both right ; it 
was the planet which had moved in the interval. 

As Neptune is half as far again from the earth as 
Uranus, we can hardly expect to learn much about the 
actual nature of the planet. We do know that it has 
four times the diameter of the earth, so that it exceeds 
the earth in the same proportion that the earth is larger 
than the moon. 

Like the other great planets, Neptune is also envel- 
oped with copious clouds ; in fact, it only weighs one- 
fifth part as much as it would do if it were made of 
materials as substantial as are those of the earth. Like 
our earth, Neptune is attended by one moon, which 
revolves round the planet in a little more than six 
days. 

The orbit of this great planet marks the boundary 



254 STAR-LAND. 

of our known system of planets. We have seen how 
the five great planets of antiquity have been increased 
in these modern days by the addition of two more, 
Uranus and Neptune, while the discovery of a multitude 
of small planets has given a further increase to the num- 
ber of the sun's family. We have still some other 
objects in our solar system to describe ; some of them 
are excessively big; these are the comets. Some of 
them are exceedingly small; they are the shooting 
stars. We shall talk about comets and shooting stars 
in our next lecture. 



LECTURE V. 

COMETS AND SHOOTING STARS. 

The Movements of a Comet — Encke's Comet — The Great Comet of Halley 

— How the Telegraph is used for Comets — The Parabola — The Mate- 
rials of a Comet — Meteors — What becomes of the Shooting Stars — 
Grand Meteors — The Great November Showers — Other Great Showers 

— Meteorites. 

THE MOVEMENTS OF A COMET. 

The planets are all massive globes, more or less flat- 
tened at the Poles ; but now we have to talk about a 
multitude of objects of the most irregular shapes, and 
of the most flimsy description. We call them comets, 
and they exist in such numbers that an old astronomer 
has said " there were more comets in the sky than 
fishes in the sea," though I think we cannot quite 
believe him. There is also another wide difference 
between planets and comets: planets move round in 
nearly circular ellipses, and not only do we know where 
a planet is to-night, but we know where it was a month 
ago, or a hundred years ago, or where it will be in a 
hundred years or a thousand years to come. All such 
movements are conducted with conspicuous regularity 
and order ; but now we are to speak of bodies which 
generally come in upon us in the most uncertain and 
irregular fashion. They visit us we hardly know whence, 
except that it is from outer space, and they are adorned 
in a glittering raiment, almost spiritual in its texture. 

255 



256 STAR-LAND. 

They are always changing their appearance in a baffling, 
but still very fascinating manner. If an artist tries to 
draw a comet, he will have hardly finished his picture 
of it in one charming robe before he finds it arrayed in 
another. The astronomer has also his complaints to 
make against the comets. I have told you how thor- 
oughly we can rely on the movements of the planets, 
but comets often play sad pranks with our calculations. 
They sometimes take the astronomers by surprise, and 
blaze out with their long tails just when we do not 
expect them. Then by way of compensation they fre- 
quently disappoint us by not appearing when they have 
been most anxiously looked for. 

After a voyage through space the comet at length 
begins to draw in towards the central parts of our sys- 
tem, and as it approaches the sun, its pace becomes 
gradually greater and greater; in fact, as the body 
sweeps round the sun the speed is sometimes 20,000 
times faster than that of an express train. It is some- 
times more than 1000 times as fast as the swiftest of 
rifle bullets, occasionally attaining the rate of 200 miles 
a second. The closer the comet goes to the sun, the 
faster it moves ; and a case has been known in which a 
comet, after coming in for an incalculable duration of 
time towards the sun, has acquired a speed so tremen- 
dous, that in two hours it has whirled round the sun and 
has commenced to return to the depths of outer space. 
This terrific outburst of speed does not last long. A 
pace which near the sun is 20,000 times that of our 
express trains diminishes to 10,000 times, to fifty times, 
to ten times that pace ; while in the outermost part of 



A COMET'S TAIL. 257 

its path the comet seems to creep along so slowly that 
we might think it had been fatigued by its previous 
exertions. 

We have so often seen a stream of sparks stretching 
out along the track of a sky-rocket, that we might nat- 




Fig. 72. — How the Comet's Tail is disposed. 

urally suppose the tail of a comet streamed out along 
its path in a somewhat similar manner. This would be 
quite wrong. You see from Fig. 72 that the tail does 
not lie along the comet's path, but is always directed 
outwards from the sun. If you will draw a line from 
the sun to the head of the comet and follow the direc- 
tion of the line, it shows the way in which the tail is 
arranged. You will also notice how the tail of the 
comet seems to grow in length as it approaches the 
sun. When the comet is first seen, the tail is often a 
very insignificant affair, but it shoots out with enor- 
mous rapidity until it becomes many millions of miles 



258 STAR-LAND. 

long by the time the comet is whirling round the sun. 
Those glories soon begin to wane as the comet flies out- 
ward; the tail gradually vanishes, and the wanderer 
retreats again to the depths of space in the same undec- 
orated condition as that in which it first approached. 

When a comet appears, it is always a matter of inter- 
est to see whether it is an entirely new object, or whether 
it may not be only another return of a comet which has 
paid us one or more previous visits. The question then 
arises as to how they are to be identified. Here we see 
a wide contrast between unsubstantial bodies like com- 
ets and the weighty and stately planets. Sketches of 
the various planets or of the face of the sun, though 
they might show slight differences from time to time, 
are still always sufficiently characteristic, just as a pho- 
tographic portrait will identify the individual, even 
though the lapse of years will bring some changes in 
his appearance. But the drawing of a comet is almost 
useless for identification. You might as well try to 
identify a cloud or a puff of smoke by making a picture 
of it. Make a drawing of a comet at one appearance, 
and sketch particularly the ample tail with which it is 
provided. The next time the comet comes round it 
may very possibly have two tails, or possibly no tail at 
all. We are therefore unable to place any reliance on 
the comet's personal appearance in our efforts to identify 
it. The highway which it follows through the sky 
affords the only means of recognition ; for the comet, if 
undisturbed by other objects, will never change its ac- 
tual orbit. But even this method of identification often 
fails, for it not unfrequently happens that during its 



ENCKE'S COMET. 259 

erratic movements the comet gets into fearful trouble 
with other heavenly bodies. In such cases the poor 
comet is sometimes driven so completely out of its road 
that it has to make for itself an entirely new path, and 
our efforts to identify it are plunged in confusion. It 
has happened that a second comet or even a third will 
be found in nearly the same track, but whether these 
are wholly different, or whether they are merely parts 
of the same original object, it is often impossible to 
determine. 

The great majority of comets are only to be seen 
with a telescope, and hardly a year passes without the 
detection of at least a few of these faint objects. The 
number of really brilliant comets that can be seen in a 
lifetime could, however, be counted on the fingers. 

ENCKE'S COMET. 

We have already alluded to a little body called 
Encke's comet, which was discovered by an astronomer 
at Marseilles. It was in the year 1818 that he was 
scanning the heavens with a small telescope, when an 
object attracted his attention. It was not one of those 
grand long-tailed comets which every one notices; this 
body was so faint that it merely appeared as a very 
small cloud of light, and was recognized as a comet by 
the fact that it was moving, It happens that there are 
other bodies in the sky very like comets ; we call them 
nebulae, and we shall have something to say about them 
afterwards. But it is remarkable that just as a planet 
is liable to be mistaken for a star, so a comet is liable 



260 STAR-LAND. 

to be mistaken for a nebula. However, in each case 
the fact of its movement is the test by which the planet 
or the comet is at once detected. A nebula stays 
always in the same spot, like a star, while a comet is 
incessantly moving. In fact, with a telescope you can 
actually watch a comet stealing past the stars that lie 
near it. You know that an object a very long way off 
may appear to move slowly, though in reality it is mov- 
ing very rapidly. Look at a steamer near the horizon 
at sea. In the course of a minute or two it will not 
appear to have shifted its position to any appreciable 
extent, but that is because it is far off. If you were 
near the ship, you would see that it was dashing along 
at the rate of perhaps fifteen or twenty miles an hour. 
In a similar manner the comet seems to move slowly, 
because it is at such a great distance. As a matter of 
fact it is moving faster at the time we see it than any 
steamer, faster than any express train, faster than any 
cannon-ball. There were special reasons why the move- 
ments of Encke's comet should be watched with peculiar 
care, and the track which it pursued be ascertained. If 
you can observe a comet three times and measure its 
position in the sky, the movement of that comet is 
completely determined. Perhaps I should say would 
be determined if the comet were let alone, which, un- 
fortunately, is not often the case. Indeed, you may 
remember how I told you some of the misadventures 
of this very comet when we were speaking about the 
planet Mercury. Encke's comet comes round in a period 
of a little more than three years, and it gives us some 
curious information that has been ascertained during 



IN OPEN SPACE. 



261 



its journeys. One of the facts we have thus learned is 
so important that we cannot omit to notice it (Fig. 73). 



Jupiter 




Fig. 73. — The Orbit of Encke's Comet. 

At increasing heights above the earth's surface there 
is gradually less and less air; until at last, at about 
200 or 300 miles above the surface on which we dwell, 
there would be none. You might as well try to quench 
your thirst by drinking out of an empty cup as attempt 



262 STAR-LAND. 

to breathe in the open space which begins a few hun- 
dred miles aloft. In open space motion could take 
place quite freely. Down here the resistance of the 
air is a great impediment to movement, especially when 
very rapid. A heavy cannon-ball is checked and robbed 
of its pace by having to plough its way through our 
dense atmosphere. The motion is arrested in the same 
way, though not of course to the same degree, as if the 
cannon-ball had been fired into water. Unsubstantial 
objects are, of course, impeded by the air to a far 
greater extent than such heavy bodies as cannon-balls. 
You know that you cannot throw a handful of feathers 
across the road in the same way that you could throw 
a handful of gravel. The light feathers cannot force 
their way through the air so well as the pebbles. A 
body so flimsy as a comet would never be able to push 
its way through an atmosphere like ours ; but out in 
empty space the comet meets with no resistance during 
the greater part of its path. Accordingly, though it has 
little more substance than a will-o'-the-wisp, the comet 
pursues its journey with as much resolute dignity as 
if it were made of cast iron. If in any part of its track 
the body should have to pierce its way through any 
material like even the thinnest possible air, then the 
unsubstantial nature of the cometary materials would 
be at once shown. The motion would be impeded, and 
the body's path would be changed. In this way a comet 
may be made very instructive, for it will show whether 
space is really so empty as we sometimes suppose it to 
be. During the greater part of its course the flimsy 
little Encke tears along with such ease and speed that 



HALLEY'S COMET. 263 

there seems to be nothing to impede it, and thus we 
learn that space is generally empty. However, when 
the comet begins to wheel around the sun, the freedom 
of its movements seems to receive a check. The un- 
substantial object has to force its way with a difficulty 
that it did not experience so long as it was moving 
round the greater part of its orbit. We thus learn that 
there is a thin diffused atmosphere surrounding the sun. 
We cannot, indeed, say that it is like our air. Its com- 
position is quite different, and almost the only way we 
know of its existence is by the evidence which this 
comet affords. In a former lecture I showed how 
Encke's comet told us the mass of the planet Mercury. 
Now we see how the travels of the same body give us 
information about the sun himself. I ought, however, 
to add that some more recent observations seem not to 
have confirmed the belief that there is the resistance of 
the kind we have just been considering. 

THE GREAT COMET OF HALLEY. 

I dare say you would think it more interesting to 
talk about some big and bright comets rather than 
about objects so faint as that of Encke. It unfortu- 
nately happens that most of the fine comets pay our 
system only a single visit. There is only one of the 
really splendid objects of this kind that comes back to 
us with anything like regularity. 

It was last seen in the year 1835, and I am glad to 
tell you that it is coming again ; it is expected about 
the year 1910. You may ask, How can we feel sure 



264 STAK-LAND. 

that such a prediction as I have mentioned will turn 
out correctly? The fact is that this comet has been 
watched for a great many centuries. We find ancient 
records, some of them nearly 2000 years old, of the 
appearance of grand comets, and several of these are 
found to fit in with the supposition that there is a 
body which accomplishes its journey in a period of 
about seventy-five or seventy-six years. Of course there 
are thousands of other comets recorded in these old 
books as well ; but what I mean is that among the 
records many are found which clearly indicate some 
successive returns of this particular body. 

I will explain how the movements of this comet 
were discovered. There was a great astronomer called 
Halley, who lived two hundred years ago, and in the 
year 1682 he, like every one else, was looking with 
admiration at a splendid comet with a magnificent tail 
which adorned the sky in that year. At the observa- 
tories, of course, they diligently set down the posi- 
tions of the comet, which they ascertained by carefully 
measuring it with telescopes. Halley first calculated 
the highway which this comet followed through the 
heavens, and then he looked at the list of old comets 
that had been seen before. He thus found that in 
1607 — that was, seventy-five years earlier — a great 
comet had also appeared, the path of which seemed 
much the same as that which he found for the body 
that he had himself observed. This was a remarkable 
fact, and it became still more significant when he 
discovered that seventy-six years earlier — namely, in 
1531 — another great comet had been recorded, which 



HIS PROPHECY. 265 

moved in a path also agreeing with those of 1607 and 
1682. It then occurred to Halley that possibly these 
were not three different objects, but only different 
exhibitions of one and the same, which moved round 
in the period of seventy-five or seventy-six years. 

There is a test which an astronomer can often apply 
in the proof of his theory, and it is a very severe test. 
He will not only show himself to be wrong if it fails, 
but he will also make himself somewhat ridiculous. 
Halley ventured to submit his reputation to this ordeal. 
He prophesied that the comet would appear again in 
another seventy-five or seventy-six years. He knew 
that he would, of course, be dead long before 1758 
should arrive ; but when he ventured to make the 
prediction, he said that he hoped posterity would not 
refuse to admit that this discovery had been made by 
an Englishman. 

You can easily imagine that as 1758 drew near, great 
interest was excited among astronomers to see if the 
prediction of Halley would be fulfilled. We are 
accustomed in these days to find many astronomical 
events foretold with the same sort of punctuality as we 
expect in railway time-tables. The Nautical Almanac 
is full of such prophecies, and we find them universally 
fulfilled. Even now, however, we are not able to set 
forth our time-tables for comets with the same confidence 
that we show when issuing them for the sun, the moon, 
or the stars. How astonishing, then, must Halley's 
prediction have seemed ! Here was a vast comet which 
had to make a voyage through space to the extent 
of manv hundreds of millions of miles. For three- 



266 STAR-LAND. 

quarters of a century it would be utterly invisible in the 
greatest telescopes, and the only way in which it could 
be perceived was by figures and calculations which 
enabled the mind's eye to follow the hidden body all 
around its mysterious track. For fifty, or sixty, or 
seventy years nothing had been seen of the comet, nor, 
indeed, was anything expected to be seen of it ; but as 
seventy-one, and seventy-two, and seventy-three years 
had passed, it was felt that the wanderer, though still 
unseen, must be rapidly drawing near. The problem 
was made more difficult for those skilful mathematicians 
who essayed to calculate it by the fact that the comet 
approached the thoroughfares where the planets circu- 
late ; and, of course, the flimsy object would be pulled 
hither and thither out of its path by the attractions of 
the weighty bodies. It was computed that the influence 
of Saturn alone was sufficient to delay the comet for 
more than three months, while it appeared that the 
attraction of Jupiter was potent enough to retard the 
expected event for a year and a half more. Was it not 
wonderful that mathematicians should be able to find out 
all these facts from merely knowing the track which 
the comet was expected to follow? Clairaut, who 
devoted himself to this problem, suggested that there 
might also be some disturbances from other causes of 
which he did not know, and that consequently the 
expected return of the comet might be a month wrong 
either way. Great indeed was the admiration in as- 
tronomical circles when, true to prediction, the comet 
blazed upon the world within the limits of time Clairaut 
had specified. 



HOW COMETS ARE ANNOUNCED. 267 

The remarkable fulfilment of this prophecy entitles 
us to speak with confidence about the past performances 
of this comet. Among all the apparitions of Halley's 
comet for the last two thousand years, perhaps the most 
remarkable is that which took place in the year 1066. 
I am sure you will all remember this date in your 
English history ; it was the year of the Conquest. In 
those days they did not understand astronomy as we 
understand it now ; they used to think of a comet as 
a fearful portent of evil, sent to threaten some fright- 
ful calamity ; such as a pestilence, a war, a famine, or 
something else equally disagreeable. Hence in the year 
of the Conquest the appearance of so terrific an object 
in the sky was a very significant omen. Attention was 
concentrated upon the spectacle, and a picture of Halley's 
comet as it appeared to the somewhat terrified imagina- 
tions of the people of those days has been preserved. 
There is a celebrated tapestry at Bayeux on which 
historical incidents are represented by beautifully worked 
pictures. On this fabric we have a view of Halley's 
comet in a quaint and rather ludicrous aspect. You 
will read of this comet also in the early pages of Ten- 
nyson's " Harold." 

HOW THE TELEGRAPH IS USED FOR COMETS. 

In these days the study of comets is prosecuted with 
energy. Over the world observatories are situated, and 
whenever a comet is discovered, tidings of the event 
are diffused among those likely to be interested. Sup- 
pose that one is discovered in the southern hemisphere, 



268 STAR-LAND. 

the astronomers then write to warn the northern 
observatories of the event. But comets often move 
faster than her Majesty's mails, so that the telegraph 
has to be put into requisition. The kind of message is 
one which shall show the position and the movements of 
the body. It necessarily involves a good many figures 
and words, and consequently it is desirable to abbreviate 
as much as possible for the sake of economy. There is 
a further difficulty in using the telegraph, because the 
messages are not of an intelligible description to those 
not specially versed in astronomy. Skilful as the 
telegraph clerks are, they can hardly be expected to be 
familiar with the technicalities of astronomers. The 
clerk at the receiving end is handed a message which 
he does not understand very clearly. The clerk at the 
other end does not understand the message which is 
delivered to him, and between them it has happened 
that they have transformed the message into something 
which not only they do not understand, but which, 
unfortunately, nobody else can understand either. 
These difficulties have been surmounted by an agree- 
ment between astronomers, which is so simple and 
interesting that I must mention it. 

The kind of message that expresses the place of a 
comet will consist of sentences something of this 
kind : " One hundred and twenty-three degrees and 
forty-five minutes." Surely it would be an advantage 
to be able to replace all these words by a single word, 
particularly if by doing so the risk of error would be 
diminished. This is what the astronomers' telegraphic 
arrangement enables them to accomplish. There is a 



WHAT IS A PAKABOLA? 269 

certain excellent Dictionary known as Worcester's. I 
am sure when Mr. Worcester arranged this work, he 
had not the slightest anticipation of an odd use to which 
it would occasionally be put. Every astronomer who 
is co-operating in the comet scheme must have a copy 
of the book. To send the message I have just referred 
to, he has to take up his Dictionary and look out page 
123. Then he will count down the column until he 
comes to the forty-fifth word on that page, which he 
finds to be " constituent," and according to this plan 
the message, or at least this part of it, is merely that 
one word, " constituent." The astronomer who receives 
this message and wishes to interpret it takes up his copy 
of Worcester's Dictionary and looks out for " constitu- 
ent." He sees that it is on page 123, and that it is the 
forty-fifth word down on that page ; and therefore he 
knows that the interpretation of the message is to be 
one hundred and twenty-three degrees and forty-five 
minutes. 

THE PARABOLA. 

Generally speaking, great comets come to us once 
and are then never seen again. Such bodies do not 
move in closed ovals or ellipses, they follow another 
kind of curve, like that represented in Fig. 74. It is 
one that every boy ought to know. In fact, in one of 
his earliest accomplishments he learned how to make a 
parabola. It is true he did not call it by any name so 
fine as this, but every time a ball is thrown into the air 
it describes a part of the beautiful curve which geome- 
ters know by this word (Fig. 74). In fact, you could 



270 STAR-LAND. 

not throw a ball so that it should describe any other 
curve except a parabola. No boy could throw a 
stone in a truly horizontal line. It will always curve 
down a little, will always, in fact, be a portion of a 
parabola. 

There are big parabolas and there are small ones. 
One of the shells which are thrown into a town when 
bombarded from a distance describes, as it rises and then 






/ p 



/ 



^^Mc^-^~~— 




Fig. 74. — The Path of a Projectile is a Parabola. 

slopes down again, part of a mighty parabola. So does 
a tennis ball thrown by the hand or struck by the racket; 
though here, indeed, I admit that a spin may be given 
to the ball which will somewhat detract from the sim- 
plicity of its movement. In playing baseball, a large 
part of the skill of the pitcher consists in throwing the 
ball in such a way that it shall not move in a parabola, 
but in some twisting curve by which he hopes to baffle 
his adversary. Setting aside these exceptions, and such 
another as the case of a body tossed straight up or 



THE USES OF THE PARABOLA. 



271 



dropped straight down, we may assert that the path of 
a projectile is a parabola. 

There are some remarkable applications of the same 
curve for practical purposes. From our lighthouses we 
want to send beams off to sea, so as to guide ships into 
port. If we merely employed a lamp without concen- 
trating its rays, we should have a very imperfect light- 
house, for the lamp scatters light about in all directions. 




Fig. 75.-— The Lighthouse Reflector. 

Much of it goes straight up into the air, much of it 
would be directed inland; in fact, there is only an 
extremely small part of the entire number of rays that 
will naturally take the useful direction. We therefore 
require something round the lamp which shall catch 
the truant rays that are running away to idleness arid 
loss, and shall concentrate them into the direction in 



272 STAR-LAND. 

which they will be useful to the mariner. An effective 
way of doing this is to furnish the lamp with a reflector. 
On its bright surface (Fig. 75) all the rays fall which 
would otherwise have gone astray, and each of them is 
properly redirected, where the sailors can see it. It is 
essential that the mirror shall do this work accurately, 
and this it will only do when it has been truly shaped 
so as to be a parabola. 

You will remember, also, how I described to you 
the reflector which Herschel made for his great tele- 
scope. The shape of the mirror must be most accu- 
rately worked, and it, too, must have a parabola for its 
section; so that you see this curve is one of impor- 
tance in a variety of ways. 

But the grandest of all parabolas are those which 
the comets pursue. Unlike the ellipse, the parabola 
is an open curve ; it has two branches stretching away 
and away forever, and always getting further apart. 
Of course, in the examples of this curve that I have 
given it is only a small part of the figure that is con- 
cerned. When you throw a stone it only describes that 
part of the parabola that lies between your hand and 
the spot where the stone hits the ground. It is just a 
part of the curve in the same way that a crescent may 
be a bit of a circle. It is to comets that we must look 
for the most complete illustration of the ample extent 
of a parabola. 

The shape of this grand curve will explain why so 
many comets only appear to us once. It is quite clear 
that if you begin to run round a closed racecourse, you 
may, if you continue your career long enough, pass 



WHY COMETS VISIT US. 273 

and repass the starting-post thousands of times. Thus, 
comets which move in ellipses, and are consequently 
tracing closed curves, will pass the earth times without 
number. For this reason we may see them over and 
over again, as we do Encke's comet or Halley's comet. 
But suppose you were travelling along a road which, 
no matter how it may turn, never leads again into 
itself, then it is quite plain that, even if you were to 
continue your journey forever, you can never twice 
pass the same house on the roadside. That is exactly 
the condition in which most of the comets are moving. 
Their orbits are parabolas which bend round the sun ; 
and, generally speaking, the sun is very close to the 
turning-point. The earth is also, comparatively speak- 
ing, close to the sun ; so that while the comet is in that 
neighborhood we can sometimes see it. We do not see 
the comet for a long time before it approaches the sun, 
or for a long time after it has passed the sun. All we 
know, therefore, of its journey is that the two ends of 
the parabola stretch on and on forever into space. The 
comet is first perceived coming in along one of these 
branches to whirl round the sun ; and after doing so, 
it retreats along the other branch, and gradually sinks 
into the depths of space. 

Why one of these mysterious wanderers should 
approach in such a hurry, and then why it should 
fly back again, can be partially explained without the 
aid of mathematics. 

Let us suppose that, at a distance of thousands of 
millions of miles, there floated a mass of flimsy material 
resembling that from which comets are made. Notwith- 



274 STAR-LAND. 

standing its vast distance from the sun, the attraction 
of that great body will extend thither. It is true the 
pull of the sun on the comet will be of the feeblest and 
slightest description, on account of the enormously great 
distance. Still, the comet will respond in some degree, 
and will commence gradually to move in the direction 
in which the sun invites it. Perhaps centuries, or per- 
haps thousands, or even tens of thousands, of years will 
elapse before the object has gained the solar system. 
By that time its speed will be augmented to such a 
degree, that after a terrific whirl around the sun, it 
will at once fly off again along the other branch of the 
parabola. Perhaps you will wonder why it does not 
tumble straight into the sun. It would do so, no doubt, 
if it started at first from a position of rest ; generally, 
however, the comet has a motion to begin with which 
would not be directed exactly to the luminary. This it is 
which causes the comet to miss actually hitting the sun. 
It may also be difficult to understand why the sun 
does not keep the comet when at last it has arrived. 
Why should the wandering body be in such a hurry 
to recede? Surely it might be expected that the 
attraction of the sun ought to hold it. If something 
were to check the pace of the comet in its terrific 
dash round the sun, then, no doubt, the object would 
simply tumble down into the sun and be lost. The 
sun has, however, not time to pull in the comet when 
it comes up with a speed 20,000 times that of an 
express train. But the sun does succeed in altering 
the direction of the motion of the comet, and the 
attraction has shown itself in that way. 



AN ELONGATED ELLIPSE. 275 

I can illustrate what happens in this manner. Here 
is a heavy weight suspended from the ceiling by a wire ; 
it hangs straight down, of course, and there it is kept 
by the pull of the earth. Supposing I draw the weight 
aside and allow it to swing to and fro, then the motion 
continues like the beat of a pendulum. The weight is 
always pulled down as near to the earth as possible, 
but when it gets to the lowest point, it does not stay 
there, it goes through that point, and rises up at the 
other side. The reason is that the weight has acquired 
speed by the time it reaches the lowest point ; and that, 
in virtue of its speed, it passes through the position in 
which it would naturally rest, and actually ascends the 
other side in opposition to the earth's pull, which is 
dragging it back all the time. This will illustrate how 
the comet can pass by and even recede from the body 
which is continually attracting it. 

Just a few words of caution must be added. Suppose 
you had an ellipse so long that the comet would take 
thousands and thousands of years to complete a circuit, 
then the part of the ellipse in which the comet moves 
during the time when we can see it is so like a parabola, 
that we might possibly be mistaken in the matter. 
In fact, a geometer will tell us that if one end of an 
ellipse was to go further and further away, the end 
that stayed with us would gradually become more 
and more like this curve. Therefore, some of those 
comets which seem to move in parabolas may really 
be moving in extremely elongated ellipses, and thus, 
after excessively long periods of time, may come back 
to revisit us. 



276 STAR-LAND. 

THE MATERIALS OF A COMET. 

A comet is made of very unsubstantial material. 
This we can show in a very interesting manner, when 
we see it moving over the sky between the earth and 
the stars. Sometimes a comet will pass over a cluster 
of very small stars, so faint that the very lightest cloud 
that is ever in the sky would be quite sufficient to hide 
them. Yet the stars are distinctly visible right through 
the comet, notwithstanding that it may be hundreds of 
thousands of miles thick. This shows us how exces- 
sively flimsy is the substance of a comet, for while 
a few feet of haze or mist suffice to extinguish the 
brightest of stars, this immense curtain of comet stuff, 
whatever it may be made of, is practically transparent. 

I have often told you that we are able to weigh the 
heavenly bodies, but a comet gives us a great deal of 
trouble. You see that the weighing machine must be 
of a very delicate kind if you are going to weigh a very 
light object. Take, for example, a little lock of golden 
hair, which no doubt has generally a value quite inde- 
pendent of the number of grains that it contains. Sup- 
pose, however, that we are so curious as to desire to 
know its weight, then one of those beautiful balances 
in our laboratories will tell us. In fact, if you snipped 
a little fragment from a single hair, the balance would 
be sensitive enough to weigh it. If, however, you were 
only provided with a common pair of scales like those 
which are suited for the parcel post, then you could 
never weigh anything so light as a lock of hair. You 
have not small enough weights to begin with, and even 



WHAT A COMET IS MADE OF. 277 

if you had they would be of no use, for 'the scale is too 
coarse to estimate such a trifle. This is precisely the 
sort of difficulty we experience when we try to weigh 
a comet. The body, though so big, is very light, and 
our scales are so cumbersome that we are in a position 
of one who would try to weigh a lock of hair with a 
parcel-post balance. We cannot always find suitable 
scales for weighing celestial bodies. We have to use 
for the purpose whatever methods of discovering the 
weights happen to be available. So far, the methods 
I have mentioned are of the rudest description; they 
serve well enough for weighing heavy masses like 
planets, but *they will not do for such unsubstantial 
bodies as comets. 

But, though we fail in this endeavor, i.e. to weigh 
comets, yet skilful astronomers have succeeded in some- 
thing which at first you might think to be almost 
impossible. They have actually been able to discover 
some of the ingredients of which a comet is made. 
This is so important a subject that I must explain it 
fully. 

The most instructive comet which we have seen in 
modern days is that which appeared in the year 1882. 
It was an object so great that its tail alone was double 
as long as from the earth to the sun. It was discovered 
at the observatories in the southern hemisphere early in 
September of that year. A little later it was observed 
in the northern hemisphere in extraordinary circum- 
stances. It must be remembered that a comet is gener- 
ally a faint object, and that even those comets which 
are large enough and bright enough to form glorious 



278 STAR-LAND. 

spectacles in the sky at night are usually invisible dur- 
ing the brightness of day. For a comet to be seen in 
daylight was indeed an unusual occurrence ; but on 
the forenoon of Sunday, September 17, Mr. Common 
at Ealing saw a great comet close to the sun. Unfor- 
tunately clouds intervened, and he was prevented from 
observing the critical occurrence just approaching. An 
astronomer at the Cape of Good Hope — Mr. Finlay — 
who had also been one of the earliest discoverers of the 
comet, was watching the body on the same day. He 
followed it as it advanced close up to the sun ; bright 
indeed must that comet have been which permitted 
such a wonderful observation. At the sun's edge the 
comet disappeared instantly ; in fact, the observers 
thought that it must have gone behind the sun. They 
could not otherwise account for the suddenness with 
which it vanished. This was not what really happened. 
It was afterwards ascertained that the comet had not 
passed behind the sun ; it had, indeed, come between 
us and our luminary. In its further progress this body 
showed in a striking degree the incoherent nature of 
the materials of which a comet is composed. It seemed 
to throw off portions of its mass along its track, each 
of which continued an independent journey. Even the 
central part in the head of the comet — the nucleus, as 
it is called — showed itself to be of a widely different 
nature from a substantial planetary body. The nucleus 
divided into two, three, four, or even five distinct parts, 
which seemed, in the words of one observer, to be con- 
nected together like pearls on a string. 

The comet of 1882 was also very instructive with 



THE COMET OF 18S2. 279 

regard to the actual materials from which such bodies 
are made. Astronomers have a beautiful method by 
which they find out the substances present in a heavenly 
body, even though they never can get a specimen of 
the body into their hands. We know at least three 
materials which were present in this comet. The first 
of them is an ingredient which is very commonly found 
in comets — a chemist calls it carbon. It is an ex- 
tremely familiar material on the earth ; for instance, 
coal is chiefly composed of carbon. Charcoal when 
burned leaves only a few ashes. All the substance that 
has vanished during combustion is carbon ; in fact, it is 
not too much to say that carbon is found abundantly 
not only in wood, but in almost every form of vegetable 
matter. The food we eat contains abundant carbon, 
and it is an important constituent in the building up 
of our own bodies. Generally speaking, carbon is not 
found in a pure state — it is associated with other sub- 
stances. Soot and lampblack are largely composed of 
it ; but the purest form of this element carbon that we 
know is the diamond. 

It is interesting to note that carbon is certainly found 
as a frequent constituent of comets. The great comet 
of 1882 undoubtedly contained it, as well as certain 
other substances. Of these we know two : the first is 
the element sodium, an extremely abundant material 
on earth, inasmuch as the salt in the sea is mainly com- 
posed of it. It was also discovered that the same great 
comet contained another substance very common here 
and extremely useful to mankind. Dr. Copeland and 
Dr. Lohse at Dunecht showed that iron was present in 



280 STAR-LAND. 

this body which had come in to visit us from the depths 
of space. 

These discoveries are especially interesting because 
they seem to show the uniformity of material composing 
our system. We already knew that sodium and iron 
abounded in the sun, and now we have learned that 
these bodies and carbon as well are present in the 
comets. In the next chapter we shall learn that the 
very same materials — sodium and iron — are met with 
in bodies far more remote from us than any bodies of 
our own system. 

Comets have such a capricious habit of dashing into 
the solar system at any time and from any direction, 
that it is worth while asking whether a comet might 
not sometimes happen to come into collision with the 
earth. There is nothing impossible in such an occur- 
rence. There is, however, no reason to apprehend that 
any disastrous consequences would ensue to the earth. 
Man has lived on this globe for many, many thousands 
of years, and the rocks are full of the remains of fossil 
animals which have flourished during past ages ; indeed, 
we cannot possibly estimate the number of millions of 
years that have elapsed since living things first crawled 
about this globe. There has never been any complete 
break in the succession of life, consequently during all 
those millions of years we are certain that no such dire 
calamity has happened to the earth as a frightful colli- 
sion would have produced, and we need not apprehend 
any such catastrophe in the future. 

I do not mean, however, that harmless collisions with 
comets may not have occasionally happened; in fact, 



COMETS AND THE EARTH. 281 

there is good reason for knowing that they have actually 
taken place. In the year 1861 a fine comet appeared ; 
and it is not so well remembered as its merits deserve, 
because it happened, unfortunately for its own renown, 
to appear just three yea*s after the comet of 1858, 
which was one of the most gorgeous objects of this kind 
in modern times. But in 1861 we had a novel experi- 
ence. On a Sunday evening in midsummer of that 
year, we dashed into the comet, or it dashed into us. 
We were not, it is true, in collision with its densest 
part ; it was rather the end of the tail which we 
encountered. There were, fortunately, no very serious 
results. Indeed, most of us never knew that anything 
had happened at all, and the rest only learned of the 
accident long after it was all over. For a couple of 
hours that night it would seem that we were actually 
in the tail of the comet, but so far as I know no one 
was injured or experienced any alarming inconvenience. 
Indeed, I have only heard of one calamity arising from 
the collision. A clergyman tells us that at midsummer 
he was always able in ordinary years to read his sermon 
at evening service without artificial light. On this 
particular occasion, however, the sky was overcast with 
a peculiar glow, while the ordinary light was so much 
interfered with that the sexton had to provide a pair of ' 
candles to enable him to get through the sermon. The 
expense of those candles was, I believe, the only loss to 
the earth in consequence of its collision with the comet 
of 1861. 

The tail of a comet appears to develop under the 
influence of the sun. As the wandering body approaches 



282 STAR-LAND. 

the source of central heat it grows warm, and as it gets 
closer and closer to the sun, the fervor becomes greater 
and greater, until sometimes the comet experiences a 
heat more violent than any we could produce in our 
furnaces. The most infusible substances, such as stones 
or earth, would be heated white-hot and melted, and 




How the Tail of a Comet arises. 



even driven off into vapor, under the intense heat to 
which a comet is sometimes exposed. Comets, indeed, 
have been known to sweep round the sun so closely as 
to pass within a seventh part of its radius from the 
surface. It seems that certain materials present in the 
comet, when heated to this extraordinary temperature, 
are driven away from the head, and thus form the tail 
(Fig. 76). Hence we see that the tail consists of a 



COMETS' TAILS. 283 

stream of vaporous particles, dashing away from the 
sun as if the heat which had called them into being was 
a torment from which they were endeavoring to escape. 
The tail of a comet is, therefore, not a permanent 
part of the body. It is more like the smoke from a 
great chimney. The smoke is being incessantly renewed 
at one end as the column gets dispersed into the air at 
the other. As the comet retreats, the sun's heat loses 
its power. In the chills of space there is, therefore, no 
tail-making in progress, while the small mass of the 
comet renders it unable to gather back again by its 
attraction the materials which have been expelled. 
Should it happen that the comet moves in an elliptic 
orbit, and thus comes back time after time to be invig- 
orated by a good roasting from the sun, it will, of 
course, endeavor to manufacture a tail each time that it 
approaches the source of heat. The quantity of mate- 
rial available for the formation of tails is limited to the 
amount with which the comet originally started ; no 
fresh supply can be added. If, therefore, the comet 
expends a portion of this every time it comes round, an 
inevitable consequence seems to follow. Suppose a boy 
receives a sovereign when he goes back to school, and 
that every time he passes the pastry-cook's shop some of 
his money disappears in a manner that I dare say you 
can conjecture, I need not tell you that before long the 
sovereign will have totally vanished. In a similar way 
comets cannot escape the natural consequences of their 
extravagance ; their store of tail-making substance must, 
therefore, gradually diminish. At each successive return 
the tails produced must generally decline in size and 



284 STAR-LAND. 

magnificence, until at last the necessary materials have 
been all squandered, and we have the pitiful spectacle 
of a comet without any tail at all. 

The gigantic size of comets must excite our astonish- 
ment. A pebble tossed into a river would not be more 
completely engulfed than is our whole earth when it 
enters the tail of one of these bodies. But we now 
pass by a sudden transition to speak of the very small- 
est bodies, of little objects so minute that you could 
carry them in your waistcoat pocket. You will perhaps 
be surprised that such things can play an important 
part in our system and have a momentous connection 
with mighty comets. 

METEORS. 

If you look out from your window at the midnight 
sky, or take a walk on a fine clear night, you will occa- 
sionally see a streak of light dash over the heavens, 
thus forming what is called a falling, or a shooting, 
star (Fig. 77). It is not really one of the regular stars 
that has darted from its place. The objects we are now 
talking of are quite different from stars proper. To 
begin with, the shooting stars are comparatively close to 
us when we see them, and they are very small, whereas 
the stars themselves are enormous globes, far bigger 
than our earth, or often even bigger than the sun. 
Sometimes a great shooting star is seen which makes 
a tremendous blaze of light as bright as the moon, or 
even brighter still. These objects we call meteors, and 
you will be very fortunate if you can ever see a really 



SHOOTING STARS. 285 

fine one. Astronomers cannot predict these things as 
they predict the appearance of the planets. Bright 
meteors consequently appear quite unexpectedly, and 
it is a matter of chance as to who shall enjoy the privi- 




Fig. 77. — A Brilliant Meteor. 

lege of beholding them. But it is not about the great 
meteors that we are now going to speak particularly; 
they are often not so interesting as the small ones. 

These little meteoroids, as we shall call them, have 
a curious history. They become visible to us only at 
the very last moment of their existence — in fact, the 
streak of light which forms a shooting star is merely 
the destruction of a meteoroid. You must always re- 
member that we are here living at the bottom of a great 
ocean of air, and above the air extends the empty space. 
Air is a great impediment to motion; a large part of 
the power of a locomotive engine has to be expended 
solely in pushing the air out of the way so as to allow 



286 STAR-LAND. 

the train to get through. The faster the speed, the 
greater is the tax which the air imposes on the moving 
body. A cannon-ball, for instance, loses an immensity 
of its speed, and consequently of its power, by having 
to bore its way through the air. In outer space beyond 
the limits of this atmosphere, a freedom of movement 
can be enjoyed of which we know nothing down here. 
I spoke of this when discussing the movements of 
Eneke's comet. Even this very unsubstantial body 
could dash along without appreciable resistance until 
it traversed the atmosphere surrounding the sun. But 
now we have to speak of the motion of a little object 
both small and dense, resembling perhaps a pebble or 
a fragment of iron, or some substance of that descrip- 
tion. It is a little body such as this which produces a 
shooting star. 

For ages and ages the meteoroid has been moving freely 
through space. The speed with which it dashes along 
greatly exceeds that of any of the motions with which 
we are familiar. It is about 100 times as swift as the 
pace of a rifle-bullet. About twenty miles would be 
covered in a second. You can hardly imagine what 
that speed is capable of. Suppose that you put one of 
these flying meteoroids beside an express train to race 
from London to Edinburgh, the meteoroid would have 
won the race before the train had got out of the station. 
Or suppose that a shooting star determined to make the 
circuit of the earth, it might, so far as pace is concerned, 
go entirely around the globe and back to the point from 
which it started in a little more than twenty minutes. 
But the fact is, you could not make any object down 



THE SPEED OF A SHOOTING STAR. 287 

here move as fast as a shooting star. No gunpowder 
that could be made would be strong enough, in the first 
place, and even if the body could once receive the speed, 
it would never be able to force its way through the air 
uninjured. 

So long as a little shooting star is tearing away 
through open space we are not able to see it. The 
largest telescope in the world would not reveal a 
glimpse of anything so small. The meteoroid has no 
light of its own, and it is not big enough to exhibit 
the light reflected from the sun in the same manner as 
a little planet would do. It is only at the moment 
when it begins to be destroyed that its visibility com- 
mences. If the little object can succeed in dashing 
past our earth without becoming entangled in the at- 
mosphere, then it will pursue its track with perhaps only 
a slight alteration in its path, due to the pull exercised 
by the earth. The air which surrounds our globe may 
be likened to a vast net, in which if any little meteor 
becomes caught its career is over. For when the little 
body, after rejoicing in the freedom of open space, dashes 
into air, immediately it experiences a terrific resistance ; 
it has to force the particles of air out of the way so as 
to make room for itself, and in doing so it rubs against 
them with such vehemence that heat is produced. 

I am sure every boy knows that if he rubs a button 
upon a board it becomes very hot, in consequence of 
the friction. There are many other ways in which we 
can illustrate the production of heat in the same man- 
ner. One is a contrivance by which we spin round 
rapidly a piece of stick pressed against a board. Quan- 



288 STAR-LAND. 

tities of heat are thus produced by the friction, and 
volumes of smoke rise up. We have read how some 
savages are able to produce fire by means of friction 
in a somewhat similar manner, but to do so requires a 
rare amount of skill and patience. There is another 
illustration by which to show how heat can be produced 
by friction. A brass tube full of water is so arranged 
that it can be turned around very rapidly by the whirling 
table. We apply pressure to the tube, and after a minute 
or two the water begins to get hot, and then at last to boil, 
until ultimately the cork is driven out and a diminu- 
tive and, fortunately, harmless explosion of the friction 
boiler takes place. Engineers are aware how frequently 
heat is produced by friction, when it is very inconven- 
ient or dangerous. Indeed, unless the wheels of railway 
carriages are kept well greased, the rubbing of the axle 
may generate so much heat that conflagrations in the 
carriage will ensue. Nature, in the little shooting star, 
gives us a striking illustration of the same fact. Per- 
haps you may be surprised to hear that the whole bril- 
liancy of the shooting star is simply due to friction. 
As the little body dashes through the air it becomes first 
red-hot, then white-hot, until at last it is melted and 
turned into vapor. Thus is formed that glowing streak 
which we, standing very many miles below, see as a 
shooting star. 

A bullet when fired from a rifle will fly into pieces 
after it has struck against the target, and if you quickly 
pick up one of these pieces you will generally find it 
quite hot. Whence comes this heat ? The bullet, of 
course, was cold before the rifleman pulled the trigger, 



THE HEAT PRODUCED BY FRICTION. 289 

No doubt there was a considerable amount of heat 
developed by the burning of the gunpowder, but the 
bullet was so short a time in contact with the wad, 
through which so little heat would pass, that we must 
look to some other source for the warmth that has been 
acquired. Friction against the barrel as the bullet 
passed to the mouth must have warmed the missile a 
good deal, and when rubbing against the air the same 
influence must have added still further to its tempera- 
ture, while the blow against the target would finally 
warm it yet more. 

In comparing the shooting star with the rifle-bullet 
we must remember that the celestial object is travelling 
with a pace 100 times as swift as the utmost velocity 
that the rifle can produce, and the heat which is gener- 
ated by friction is increased in still greater proportion. 
If we double the speed, we shall increase the quantity of 
heat by friction fourfold ; if we increase the speed three 
times, then friction will be capable of producing nine 
times as much heat. In fact, we must multiply the 
number expressing the relative speed by itself — that 
is, we must form its square — if we want to find an 
accurate measure for the quantity of heat which friction 
is able to produce when a rapidly moving body is being 
stopped b}r its aid. The shooting star may have a pace 
100 times that of the rifle-bullet, and if we multiply 100 
by 100 we get 10,000 ; consequently we see that the 
heat produced by the shooting star before its motion 
was arrested in dashing through the air would be 
10,000 times that gained by the rifle-bullet in its flight. 
If the temperature of the rifle-bullet only rose a single 



290 STAR-LAND. 

degree by friction, it would thus be possible for the 
shooting star to gain 10,000 degrees, and this would 
be enough to melt and boil away any object which ever 
existed. Thus we need not be surprised that friction 
through the air, and friction alone, has proved an ade- 
quate cause for the production of all the heat necessary 
to account for the most brilliant of meteors. 

■ It is rather fortunate for us that the meteors do dash 
in with this frightful speed ; had the little bodies only 
moved as quickly as a rifle-bullet, or even only four or 
five times as fast, they would have pelted down on the 
earth in solid form. Indeed, on rare occasions it does 
happen that bodies from the heavens strike down on the 
ground. The great majority of those that fall on the 
ground, however, become entirely transformed into 
harmless vapor. The earth would, indeed, be almost 
uninhabitable from this cause alone were it not for the 
protection that the air affords us. All day and all 
night innumerable missiles would be whizzing about us, 
and though many of them are undoubtedly very small, 
yet as their speed is 100 times that of a rifle-bullet, the 
fusillade would be very unpleasant. It is, indeed, the 
intense hurry of these celestial bullets to get at us 
which is the very source of our safety. It dissipates 
the meteors into streaks of harmless vapor. 

WHAT BECOMES OF THE SHOOTING STARS. 

When we throw a lump of coal on the fire, all that 
is soon left is a little pinch of ashes, and the rest of 
the coal has vanished. You might think it had been 



WHAT BECOMES OE METEORS. 291 

altogether annihilated, but that is not nature's way. 
Nothing is ever completely destroyed ; it is merely 
transformed or changed into something else. The 
greater part of the coal has united with the oxygen 
which it has obtained from the air, and has formed 
a new gas, which has ascended the chimney. Every 
particle that was in the coal can be thus accounted for, 
and in the act of transformation heat is given out. 

A meteor also becomes transformed, but the sub- 
stance it contains is not lost, though it is changed into 
glowing vapors. It is known that with heat enough 
any substance can be turned into vapor, just as water 
can be boiled into steam. Look at an electric light 
flashing between two pieces of carbon. Though carbon 
is one of the most difficult substances to melt, yet such 
is the intense heat generated by the electric current 
that the carbon is not only melted, but is actually 
turned into a vapor, and it is this vapor glowing with 
heat that gives us the brilliant light. In a similar man- 
ner iron can be rendered red-hot, white-hot, and then 
boiled and transformed into an iron vapor, if we may so 
call it. There is, indeed, plenty of such iron vapor in 
the universe. Quantities of it surround the sun and 
some of the stars. 

When ordinary steam is chilled it condenses into 
little drops of water. So, too, if iron be heated until 
it is transformed into vapor, and if that vapor be 
allowed to condense, it will ultimately form a dust, 
consisting of bits of iron so small that you would 
require a microscope to examine them. There is iron 
present in the small shooting stars. Other substances 



292 STAR-LAND. 

are also contained therein, and all these materials, 
after being boiled by the intense heat, are transformed 
into vapor. When the heat subsides, the vapor con- 
denses again into fine dust, so that the ultimate effect 
of the atmosphere on a shooting star is to grind the 
little object into excessively fine powder, which is scat- 
tered along the track which the object has pursued. 
Sometimes this powder will continue to glow for min- 
utes after the meteor has vanished, and in the case of 
some great meteors this stream of luminous dust in the 
air forms a very striking spectacle. A great meteor, or 
fire-ball as it is often called, appeared on the 6th of 
November, 1869. It flew over Devonshire and Corn- 
wall, and left a track fifty miles long and four miles 
wide. The dust remained visible all along the great 
highway for nearly an hour ; it formed a glowing cloud 
hanging in the sky, and though originally nearly straight, 
it became bent and twisted by the winds before it finally 
disappeared from view. 

We have now to see what becomes of this meteoric 
dust which is being incessantly poured into the air from 
external space. None of it ever gets away again ; for 
whenever an unfortunate meteor just touches the air it 
is inevitably captured and pulverized. That dust sub- 
sides slowly, but we do not find it easy to distinguish 
the particles which have come from the shooting stars, 
because there is so much floating dust which has come 
from other sources. 

A sunbeam is the prettiest way of revealing the 
existence of the motes with which the air is charged. 
The sunbeam renders these motes visible exactly in the 



MOTES EVERYWHERE IN THE AIR. 293 

same way as planets become visible when sunbeams 
fall on them in far-distant space. But if we have not 
the sunbeams here, we can throw across the room a 
beam of electric light, and it is seen glowing all along 
its track, simply because the air of the room, like air 
everywhere, is charged with myriads of small floating 
particles. If you hold the flame of a spirit-lamp 
beneath this beam, you will see what seems like col- 
umns of black smoke ascending through it. But these 
columns are not smoke, they are pure air, or rather air 
in which the solid particles have been transformed into 
vapor by the heat from the spirit-flame. 

The motes abound everywhere in the air. We take 
thousands of them into our lungs every time we breathe. 
They are on the whole gradually sinking and subsiding 
downwards, but they yield to every slightest current, 
so that when looking at a sunbeam you will find them 
moving in all directions. It is sometimes hard to 
believe that the little objects are tending downwards, 
but if you look on the top of a book that has lain for a 
time on a book-shelf, you find there a quantity of dust, 
produced by the motes which have gradually subsided 
where they found a quiet spot and were allowed suffi- 
cient time to do so. 

The great majority of these particles consist, no 
doubt, of fragments of terrestrial objects. The dust 
from the roads, the smoke from the factories, and numer- 
ous other sources, are incessantly adding their objec- 
tionable particles to the air. There can be no doubt 
that the shooting stars also contribute their mites to the 
dust with which the atmosphere is ever charged. The 



294 STAR-LAND. 

motes in the murky air of our towns have no doubt 
chiefly originated from sources on this earth. Many of 
these sources it would be impossible to regard as of a 
romantic description. We may, however, feel confident 
that among those teeming myriads of small floating 
objects are many little particles which, having had their 
origin from shooting stars, are now gradually sinking 
to the earth. 

This is not a mere surmise, for dust has been col- 
lected from lofty Alpine snows, from the depths of the 
sea, and from other localities far removed from the 
haunts of men. From such collections, tiny particles 
of iron have been obtained, which have evidently been 
once in a molten condition. There is no conceivable 
explanation for the origin of iron fragments in such 
situations, except that they have been dropped from 
shooting stars. 

I am sure you have often helped in the making of a 
gigantic snowball. You begin with a small quantity 
of snow that can be worked with your hands. Then 
you have rolled it along the ground until it has become 
so big and so heavy that you must get a few playmates 
to help you, until at last it has grown so unwieldy that 
you can move it no longer, and then you apply your 
artistic powers to carving out a statue. The snowball 
has grown by the addition of material to it from with- 
out, and as it became heavier and heavier, it lapped up 
more and more of the snow as it rolled along ; so that 
with each increase of size, its capacity for becoming 
still larger has also increased. I want to liken our 
earth to a snowball which goes rolling on through 



GRAND METEORS. 295 

space, and every day, every hour, every minute, is 
gathering up and taking into it the little shooting stars 
that it meets with on its way. No doubt the annual 
accumulation is a very small quantity when compared 
with the whole size of the earth ; but the earth is 
always drawing in, and now, at all events, never giving 
back again ; so that when this process is carried on long 
enough, astonishing results may be obtained. 

You have all heard many maxims on this subject — 
how every little saving will at length reach a respect- 
able or a gigantic total. Nature abounds with illustra- 
tions of the principle. All the water that thunders 
over Niagara is merely a sufficient number of little 
drops of rain collected together. Our earth has been 
gradually hoarding up, during countless ages, all the 
meteor dust that has rained upon it ; and the larger the 
earth grows, the bigger is the net which it spreads, and 
the greater is the power it has to capture the wandering 
bodies. Thus, our earth, ages and ages ago, may have 
been considerably smaller than it is at present ; in fact, 
a large proportion of this globe on which we dwell may 
have been derived from the little shooting stars which 
incessantly rain in upon its surface. 

GRAND METEORS. 

I dare say that many of those present will, in the 
course of their lives, have opportunities of seeing some 
of the great meteors, or fire-balls, which are occasionally 
displayed. Generally speaking, about one hundred or 
so of these splendid objects are recorded every year. 



296 



STAR-LAND. 



We are never apprised that they are coming ; they take 
us unawares, and therefore we have no opportunity to 
make proper arrangements for seeing them. There is 
only the chance that such persons as have been fortu- 
nate enough to see them will have noted the circum- 
stances with sufficient accuracy to enable us to make 
use of their observations. 

The chief point to determine is the height of the 
meteor above the earth. For this we must have two 



^METEOR 



London 170 miles York 

Fig. 78. — How to find the Height of a Meteor. 



observations at least, made in places as far asunder 
as possible. Suppose an observer at London and an 
observer at York were both witnesses of a splendid 
meteor; if they find, on subsequent comparison, that 
their observations were made at the same moment, there 
is no reasonable doubt that it was the same object they 
both saw. The observer at York describes the meteor 



HOW TO FIND A METEOR'S HEIGHT. 297 

as lying to the south, halfway down from the point 
directly over his head towards the horizon. The Lon- 
don observer speaks of the meteor as being to the 
north ; and to him also it appeared that the object was 
halfway down towards his horizon from the point 
directly over his head. If you know a little Euclid, 
you can easily show from these facts that the height of 
the meteor must have been half the distance between 
London and York, that is, 85 miles (Fig. 78). 

I do not mean to say that the mode of discovering 
the meteor's height will be always quite such a simple 
process as it has been in the case of the London and 
York observations. The principle is, however, the same 
— that whenever from two sufficiently distant positions 
the direction of the meteor has been observed, its path 
is known — just as on p. 21 we showed how the 
height of the suspended ball was obtained from ob- 
servations at each end of the table. Generally speak- 
ing, bright meteors begin at an elevation of between 
fifty and one hundred miles, and they become ex- 
tinguished before they are within twenty miles of the 
ground. 

Sometimes a tremendous explosion will take place 
during the passage of a meteor through the air. There 
was a celebrated instance in America on the 21st of 
December, 1876, which will give an idea of one of these 
objects possessing exceptional magnificence. It began 
in Kansas about seventy-five miles high, and thence it 
flew for a thousand miles at a speed of ten or fifteen miles 
a second, until it disappeared somewhere near Lake 
Ontario. Over a certain region between Chicago and St. 



298 STAR-LAND. 

Louis, the great ball of fire burst into a number of pieces, 
and formed a cluster of glowing stars that seemed to 
chase each other over the sky. This cluster must have 
been about forty miles long and five miles wide, and 
when the explosion occurred a most terrific noise was pro- 
duced, so loud that many thought it was an earthquake. 
A remarkable circumstance illustrates the tremendous 
height at which this explosion occurred. The meteor 
had burst into pieces, the display was all over, and was 
beginning to be forgotten, and yet nothing had been 
heard. It was not until a quarter of an hour after the 
explosion had been seen that a fearful crash was heard 
at Bloomington. The explosion actually occurred 180 
miles from the spot, and as sound takes five seconds to 
travel a mile, you can easily calculate that the noise 
required a quarter of an hour for its journey. What a 
tremendous noise it must have been ! 

Shooting stars are of every grade of brightness. 
Beginning with the more gorgeous objects which have 
been compared with the moon or even with the sun 
himself, we descend to others as bright as Venus or as 
Jupiter ; others are as bright as stars of various degrees 
of brilliancy. Fainter shooting stars are much more 
numerous than the conspicuous ones ; in fact, there are 
multitudes of these objects so extremely feeble that the 
unaided eye would not show them. They only become 
perceptible in a telescope. It is not uncommon while 
watching the heavens at night to notice a faint streak 
of light dashing across the field of the instrument. 
This is a shooting star which is invisible except through 
the telescope. 



A SHOWER OF SHOOTING STARS. 299 

THE GREAT NOVEMBER SHOWERS. 

Occasionally we have the superb spectacle of a shower 
of shooting stars. None of you, my young friends, can 



Fig. 79. — A Great Shower of Shooting Stars. 

as yet have had the good fortune to witness one of the 
specially grand displays, but you may live in hope ; 
there are still showers to come. Astronomers have 
ventured on the prophecy that in or about the year 
1899 you will have the opportunity of seeing a mag- 



300 STAR-LAND. 

nificent exhibition of this kind. There is only one 
ground for anxiety, and that is as to whether the clouds 
will keep out of the way for the occasion. I think I 
cannot explain my subject better than by taking you 
into my confidence and showing you the reasons on 
which we base this prediction. The last great shooting- 
star shower took place in the year 1866, or, perhaps, I 
should rather say that this was the last display from 
the same shooting-star system as that about which we 
are now going to speak. On the night of the 13th of 
November, 1866, astronomers were everywhere delighted 
by a superb spectacle. Enjoyment of the wondrous 
sight was not only for astronomers. Every one who 
loves to see the great sights of nature will have good 
reason for remembering that night. I certainly shall 
never forget it. It was about ten o'clock when a bril- 
liant meteor or two first flashed across the sky, then 
presently they came in twos and threes, and later on 
in dozens, in scores, in hundreds. These meteors were 
brilliant objects, any one of which would have extorted 
admiration on an ordinary night. What, then, was the 
splendor of the display when they came on in multi- 
tudes ? For two or three hours the great shower lasted, 
and then gradually subsided. 

We were not taken unawares on this occasion, for the 
shower was expected, and had been, in fact, awaited 
with eager anticipation. It should first be noticed that 
each year some shooting stars may always be looked for 
on or about the 13th of November. Every thirty-three 
years, or thereabouts, the ordinary spectacle breaks out 
into a magnificent display. It has also been found that 



AN AWFUL SCENE. 301 

for nearly 1000 years there have been occasional grand 
showers of meteors at the time of year mentioned, 
and all these incidents agree with the supposition that 
they are merely repetitions of the regular thirty-three- 
year shower. The first was in the year a.d. 902, which 
an old chronicle speaks of as the " year of the stars," 
from the extraordinary display which then took place. 
I do not think the good people 1000 years ago fully 
appreciated the astronomical interest of such spectacles ; 
in fact, they were often frightened out of their wits, 
and thought the end of the world had come. Doubt- 
less many ancient showers have taken place of which 
we have no record whatever. In more modern days we 
have had somewhat fuller information ; for example, on 
the night between the 12th and 13th of November, 1833, 
a shower was magnificently seen in America. Mr. 
Kirkwood tells us that a gentleman of South Carolina 
described the effect on the negroes of his plantation as 
follows : "I was suddenly awakened by the most dis- 
tressing cries that ever fell on my ears. Shrieks of 
horror and cries for mercy I could hear from most of 
the negroes of the three plantations, amounting in all 
to about 600 or 800. While earnestly listening for the 
cause, I heard a faint voice near the door calling my 
name. I arose, and taking my sword, stood at the door. 
At this moment I heard the same voice still beseeching 
me to arise, and crying out that the world was on fire. 
I then opened the door, and it is difficult to say which 
excited me the most — the awfulness of the scene or 
the distressed cries of the negroes. Upwards of a 
hundred lay prostrate on the ground, some speechless, 



302 STAR-LAND. 

and some with the bitterest cries, but with their hands 
raised praying for mercy. The scene was truly awful, 
for never did rain fall much thicker than the meteors 
fell towards the earth." 

By the study of many records of great showers it 
was learned that the interval at which these grand 
displays succeeded one another was about thirty-three 
years ; and when it was remembered that the last great 
shower was in 1833 it was confidently expected that 
another similar display would take place in 1866. This 
was fully confirmed. Yet another thirty-three years 
brings us to 1899, when we have good reason for looking 
forward to a grand shower of these bodies. It may be 
expected to occur on November 14 or November 15. It 
may, however, possibly be that a shower will occur on 
the same days of the succeeding year. 

We know a good deal now as regards the movements 
of these little objects. I want you to think of a vast 
swarm, something like a flock of birds, which I dare 
say you have often seen flying high in the air ; the 
difference, however, is that the flock of meteors is 
enormously greater than any flock of birds ever was ; 
and the meteors, too, are scattered so widely apart, that 
each one may be miles away from its next neighbors. 
Usually the meteoric shoal is many millions of miles 
long, and perhaps a hundred thousand miles in width. 
The great flock of meteors travels through space in a 
certain definite track. We have learned how the sun 
guides a planet, and forces the planet to move around 
him in an ellipse. But our sun will also condescend 
to guide an object no bigger than a shooting star. A 



THE PATHS OF METEORS. 



303 



bullet, a pea, or even a grain of sand will be held to an 
elliptic course around the sun as carefully as the great 
Jupiter himself. The entire shoal of meteors may 
therefore pursue their common journey around the sun 
as if inspired by a common purpose, each individual 
member of the host being, however, guided by the sun, 




Meteors 



Fig. 80. — The Earth crossing the Track of Meteors. 

and performing its path in real independence of its 
neighbors. The orbit followed by this shoal of meteors 
is enormously large and wide. Here is a sketch of the 
path (Fig. 80), and I have laid down the position of 
the orbit of the earth, but not on the same scale. The 
ellipse is elongated, so that while the shoal approaches 
comparatively close to the sun at one end of its journey, 
at the other end it goes out to an enormous distance, 
far beyond the orbit of the earth — beyond, indeed, the 
orbit of Jupiter or Saturn ; in fact, it reaches to the 



304 STAR-LAND. 

path of Uranus. To accomplish so vast a journey as 
this thirty-three years and a quarter are required, and 
now you will be easily able to see why we get period- 
ical visits from the shoal. 

It is, however, a mere piece of good fortune that we 
ever encounter the November meteors. Probably there 
are numerous other shoals of meteors quite as impor- 
tant which we never see, just in the same way as there 
are many shoals of fish in the sea that never come into 
our net. The earth moves round the sun in a path 
which is very nearly a circle, and the shoal moves 
round in this long oval. We cannot easily represent 
the true state of things by mere diagrams which show 
all these objects on the same plane. This does not 
give an accurate representation of the orbits. I think 
you will better understand what I mean by means of 
some wire rings. Make a round one to represent the 
path of the earth, and a long oval one to represent the 
path of the meteors. There is to be a small opening in 
the circular ring so that we can slip one of the orbits 
inside the other. If we are to see the meteors, it is of 
course necessary that they should strike the earth's 
atmosphere, for they are not visible to us when they 
lie at a distance like the moon or like the planets. It 
is necessary that there be a collision between the earth 
and the shoal of meteors. But there never could be a 
collision between two trains unless the lines on which 
these trains run meet each other ; therefore, it is neces- 
sary that this long ellipse shall actually cross the 
earth's track ; it will not do to have it pass inside like 
the two links of a chain; our earth would then miss 



WHEN TO SEE THE METEORS. 305 

the meteors altogether, and we should never see them. 
There are very likely many of such shoals of meteors 
revolving in this way, and thus escaping our notice 
entirely. 

You will also understand why there is no use in 
looking for these showers except on a particular day of 
November. On that day, and on that day alone, the 
earth appears at that particular point of its route where 
the latter crosses the track of the shoal. On the 1st of 
November, for instance, the earth has not yet reached 
the point where it could meet with these bodies. By 
the end of November it has passed too far. But even 
supposing that the earth is crossing the track of the 
meteors on the 13th of November, it is still possible 
that only a few, or none at all, shall be seen. The 
shoal may not happen to be at that spot at the right 
time. For a display of meteors to occur, it is therefore 
necessary that the shoal shall happen to be passing this 
particular stage of the journey on the 13th of Novem- 
ber. In 1866 the earth dipped through the shoal and 
caught a great many of these meteors in its net. For 
a few hours the earth was engaged in the capture, 
until it emerged on the other side of the shoal, and the 
display was at an end. 

Sometimes it happens that in two years following 
each other, grand showers of meteors are seen. The 
reason of this is that the shoal is very long and thin, 
and consequently if the earth passes through the begin- 
ning of the shoal one year, it may have returned to the 
same point next year before the whole length of the 
shoal has completely passed. In this case we shall 



306 STAR-LAND. 

have two great showers in consecutive years. Thus a 
very fine display was seen in America on the proper 
day in 1867, while many stragglers were also observed 
during the three subsequent recurrences of the same 
date. 

Whenever the 13th of November comes round we 
generally meet with at least five shooting stars belong- 
ing to this same system, and we must explain how this 
occurs. Suppose there is a small racecourse so that the 
competitors will have to run a great many times round 
before the race is over. Let there be a very large num- 
ber of entries, and let the majority of the athletes be 
fairly good runners, while a few are exceptionally good 
with varying degrees of excellence, and a few are very 
bad, some being worse than others. The whole group 
starts together in a cluster at the signal, and perhaps 
for the first round or two they may keep tolerably well 
together. It will be noticed the cluster begins to elon- 
gate as one circuit after another is made ; the better 
runners draw out to the front, and the slower runners 
lag further and further behind ; at last it may happen 
that those at the head will have gained a whole round 
on those at the tail, while the other runners of varying 
degrees of speed will be scattered all round the course. 
The majority of the runners, if of nearly equal speed, 
may continue in a pretty dense group. 

Precisely similar has been the great celestial race 
which these meteors are running. They started on 
their grand career centuries ago, and ever since then 
they have been flying round and round their mighty 
course. The greater proportion of the meteors still 



THE GREAT METEOR RACE. 307 

stay close together, and their pace is nearly uniform. 
The exceptionally smart ones have shot ahead, the ex- 
ceptionally slow ones have lagged behind, and thus it 
happens that, after fifty or more revolutions have been 
completed, the shape of the original swarm has become 
considerably modified. Its length has been drawn out, 
while the stragglers and the fastest runners have been 
scattered all around the path. Across this course our 
earth carries us every November; there we usually 
encounter some of the members of this swarm which 
have strayed from the great host; they flash into the 
air, and thus it is that some of these bodies are gen- 
erally seen every November. 

During a shooting-star shower it is interesting to 
notice that all the meteors seem to diverge from a 
single point. In the adjoining figure (Fig. 81), which 
shows the directions of a number of meteors' tracks, 
you will notice that every one seems to radiate from a 
certain point of the sky. In the case of the shower of 
the 13th-15th of November this point lies in the con- 
stellation Leo. I must refer you to the Appendix for 
a description of the way to find Leo or the Lion. The 
radiant point, as we term it, of this system of meteors 
is there situated. It is true that the meteors themselves 
do not generally seem to come all the way from this 
place. It is the direction of their luminous trails pro- 
duced backward that carries the eye to the radiant 
(Fig. 81). If a meteor were actually seen there, it would 
be certainly coming straight towards us ; it would not 
then appear as a streak of light at all ; it would merely 
seem like a star which suddenly blazed into splendor and 



308 



STAR-LAND. 



then again sank down into invisibility. Every meteor 
which appeared near this point would be directed very 
nearly at the observer, and its path would therefore 
seem very much foreshortened. I can illustrate this 
with a long straight rod. If I point it directly at you, 




Fig. 81. — The Radiant. 



you can only see the end. If I point it nearly at you, 
it will seem very much shortened. During the great 
shower in 1866 many of the meteors could be observed 
so close to the radiant in Leo that they seemed merely 
like very short marks in the sky ; some of them, indeed, 
seemed to be merely starlike points swelling up into 
brilliance and then going out. Hence it is that we call 
this system of shooting stars the " Leonids." They bear 



THE LEONIDS AND THE PERSEIDS. 309 

this name because their radiant lies in the constellation 
Leo, and unless the direction of a shooting star ema- 
nates from this point it does not belong to the Leonids. 
Even if it did so, the meteor would not be a Leonid 
unless the date was right, namely, on the 13th of 
November, or within a day thereof. We thus have 
two characteristics which belong to a system of shoot- 
ing stars; there is the date on which they occur and 
the point from which they radiate. 

OTHER GREAT SHOWERS. 

To illustrate what I have said, we will speak about 
another system of shooting stars; they are due every 
August, from the 9th to the 11th, and their directions 
diverge from a point in the constellation of Perseus. 
I may remind you of the dates of the recurrence of 
this shower as well as of the November meteors of 
which we have just spoken, by quoting the following 
production : — 

If you November's stars would see, 
About the fourteenth watching be. 
In August, too, stars shine through heaven, 
On nights between nine and eleven. 

It may be worth your while to remember these lines, 
and always to keep a look-out on the days named. 
The August meteors, the Perseids we often call them, 
do not make gorgeous displays, in particular years, 
with the regularity of the Leonids. There have been, 
no doubt, some exceptionally grand showers between 
the 9th and the 11th of August, but we cannot predict 



310 STAR-LAND. 

when the next splendid one is due. There are vast 
numbers of stragglers all round the track of the Per- 
seids. In fact, it would seem as if the great race had 
gone on for such a long period that the cluster had to 
a great extent broken up, and that a large proportion of 
the meteors were now scattered the whole way around 
the course with tolerable uniformity. This being so, it 
follows that every time we cross the track we are nearly 
certain to fall in with a few of the stragglers, though we 
may never enjoy the tremendous spectacle of a plunge 
through a dense host of meteoroids. 

There are many other showers besides the two I have 
mentioned. Some shooting stars are to be seen almost 
every fine night, and those astronomers who pay par- 
ticular attention to this subject are able to make out 
scores of small showers which might not interest you. 
Each of these is fully defined by the night of the year 
on which it occurs and the position of the point in the 
heavens from which the meteors radiate. Of these I 
must mention one. It is not usually very attractive, 
but it has a particular interest, as I shall now explain. 

On the 27th of November, 1872, a beautiful meteoric 
shower took place. You will notice that though the 
month is the same, the day is entirely different from 
that on which the Leonids appear. This shower of the 
27th is called the Andromedes, because the lines of 
direction of the shooting stars of which it is composed 
seem to diverge from a point in the constellation 
Andromeda. Ordinarily speaking, there is no special 
display of meteors connected with the annual return of 
this day; but in 1872 astronomers were astonished by 



METEORS AND COMETS. 311 

an exhibition of shooting stars belonging to this sys- 
tem. They were not at all bright when compared with 
the Leonid meteors. They were, however, sufficiently 
numerous to arrest the attention of very many, even 
among those who do not usually pay much attention to 
the heavens. 

The chief interest of the shower of Andromedes 
centers in a remarkable discovery connecting meteors 
and comets. There is a comet which was discovered 
by the astronomer Biela. It is a small object, requir- 
ing a telescope to show it. This comet completes each 
revolution in a period of about seven years ; or rather, 
I should say, that was the time which the comet used 
to spend on its journey, for a life of trouble and disaster 
seems of late to have nearly extinguished the unfortu- 
nate object. In 1872 the comet was due in our neigh- 
borhood, and on the night of the 27 th of November, in 
the same year, the earth crossed the track, and, in doing 
so, the shower of shooting stars was seen. This was a 
remarkable coincidence. We crossed the path of the 
comet at the time when we knew the comet ought to 
be there ; and though we did not then see the comet, 
we saw a shower of shooting stars, and a wonderful 
shower too. A circumstance so peculiar suggested at 
once that the comet and the shooting stars must in 
some way or other be connected together. This is a 
suggestion we can test in another manner. We know 
the history of the comet, and we are aware that at the 
very time of the shower, the comet was approaching 
from the direction of the constellation of Andromeda. 
It was coming, in fact, from the very quarter whence 



312 STAK-LAND. 

the shooting stars have themselves travelled. Taking 
all these things together, it seems impossible to doubt 
that the shoal of shooting stars was, if not actually 
the comet itself, something closely connected with that 
famous body. 

METEORITES. 

Some years ago, a farmer living near Rowton, in 
Shropshire, noticed on a path in a field a hole which 
had been suddenly made by some mysterious and un- 
known agent. The laborers who were near told him 
they had just heard a remarkable noise; and when 
the farmer put his hand down into the hole, he felt 
something hot at the bottom of it. He took a spade 
and dug up the strange body, and found it to be a piece 
of iron, weighing about seven pounds. He was natu- 
rally amazed at such an occurrence, and brought the 
body home with him. 

Where did that piece of iron come from ? It is plain 
that it could not have been always in the ground. The 
noise and the recently made hole showed that was not 
the case, and that is confirmed by the fact that the iron 
was hot. A piece of iron within a few feet of the earth's 
surface cannot have remained warm for any length of 
time. It is therefore clear that the iron must have tum- 
bled from the sky. This is a marvellous notion; in 
fact, it seems so incredible that at first people refused 
to believe that such things as stones or solid lumps of 
iron could have fallen from the heavens to the earth. 
But they had to believe it; the evidence was too 



IRON HAILSTONES. 313 

conclusive. Fortunately, however, the occurrence is 
a comparatively rare one ; indeed, our life on this 
globe would have an intolerable anxiety added to it 
if showers of iron hailstones like that at Rowton were 
at all of frequent occurrence. We should want um- 
brellas of a more substantial description than those 
which suffice for the rains we actually experience. 
There are, indeed, instances on record of persons hav- 
ing been killed by the fearful blows given by these 
bodies in falling. 

The Rowton siderite is a comparatively small one ; 
pieces weighing hundredweights, and even tons, have 
been collected together in our museums. I would rec- 
ommend you to pay a visit to that interesting room 
in our great British Museum in which these meteorites 
are exhibited. There we see actual specimens of celes- 
tial bodies which we can feel or weigh, and which our 
chemists can analyze. It maybe noticed that they only 
contain substances that we already know on this earth. 
This celestial iron has often been made use of in primi- 
tive times before man understood how to smelt iron 
from its ore and how to transform it from cast iron to 
wrought iron. Nature seems to have taken heed of 
their wants, and occasionally to have thrown down a 
lump or two for the benefit of those who were so fortu- 
nate as to secure them. 

That these stones or irons drop from the sky is abso- 
lutely certain, but when we try to find out their earlier 
history we become involved in not a few difficulties. 
Nobody really knows the true history of these objects, 
but the view of their origin which seems to me to possess 



314 STAR-LAND. 

fewer difficulties than any other view is that which we 
may call the Columbiad Theory. I use this expression 
because every boy or girl listening to me ought to have 
read Jules Verne's wonderful book, " From the Earth 
to the Moon," and if any of you have not read it, the 
sooner you do so the better. It is there narrated how 
the gun club of Baltimore designed a magnificent can- 
non which was sunk deep into the ground, and then 
received a terrific charge of guncotton, on which a great 
hollow projectile was carefully lowered, containing 
inside the three adventurous explorers who desired to 
visit the moon. Calculations were produced with a 
view of showing that by firing on a particular day 
the explosion would drive the projectile up to the 
moon. There was, however, the necessary condition 
that the speed of projection should be great enough. 
The gun club were accurate in saying that if the can- 
non were able to discharge the projectile with a speed 
twenty or thirty times as great as that which had ever 
been obtained with any other cannon, then the missile 
would ascend up and up forever if no further influence 
were exerted on it. No doubt we have to overlook the 
resistance on the air and a few other little difficulties, 
but to this extent, at all events, the gun club were 
right: that a velocity of about six or seven miles a 
second would suffice to carry a body away from the 
gravitation of the earth. 

No one supposes that there were ever Columbiad 
cannons on our globe by which projectiles were shot 
up into space ; but it seems possible that there may 
have been in very ancient days volcanoes on the earth 



THE COLUMBIAD THEORY. 315 

with a shooting power as great as that which President 
Barbicane designed for the big cannon. 

Even now we have some active volcanoes of great 
energy on our earth, and we know that in former days 
the volcanoes must have been still more powerful ; that, 
in fact, the Vesuvius of the present must be merely 
a popgun in comparison with volcanoes which have 
shaken the earth in those primitive days when it had 
just cooled down from its original fiery condition. Some 
of these early volcanoes, in the throes of their mighty 
eruptions, appear to have shot forth pieces of iron and 
volcanic substances with a violence great enough to 
carry them off into space. 

Suppose that a missile were projected upwards, it 
would ascend higher and higher, and gravity would, 
of course, tend to drag it back again down to earth. 
It can be shown that with an initial speed of six or 
seven miles a second the missiles would never return 
to the earth if only influenced by its attraction. The 
subsequent history of such a projectile would be guided 
by the laws according to which a planet moves. The 
body is understood to escape the destination which was 
aimed at by the Columbiad. I mean, of course, that it 
is not supposed to hit the moon. Of course, this might 
conceivably happen ; but most of the projectiles would 
go quite wide of the mark, and would travel off into 
space. 

Though the earth would be unable to recall the pro- 
jectile, the attraction of the sun would still guide it, 
whether it was as big as a paving-stone or ever so much 
larger or smaller. The body would be constrained to 



316 STAR-LAND. 

follow a path like a little planet around the sun. This 
track it would steadily pursue for ages. The wanderer 
would, however, cross the earth's track once during 
each of its revolutions at the point from which it was 
projected. Of course, it will generally happen that the 
earth will not be there at the time the meteorite is cross- 
ing, and the meteorite will not be there at the time the 
earth is crossing. Nothing will therefore happen, and 
the object goes again on its long rounds. But sometimes 
it must occur that a meteor does not get past the junc- 
tion without coming so close to the earth that it plunges 
into the air, often producing a noise and generating a 
streak of light like a shooting star. Then it tumbles 
down, and is restored to that earth whence it originally 
came. 

If this be the true view — and I think there are less 
weighty objections to it than to any other I know of — 
then the history of the piece of iron that was found in 
Shropshire would be somewhat as follows. Many mil- 
lions of years ago, when the fires of our earth were 
much more vigorous than they are in these dull times, 
a terrific volcanic outbreak took place, and vast quan- 
tities of material were shot into space, of which this is 
one of the fragments. During all the ages that have 
since elapsed this piece of iron has followed its lonely 
track. In a thousandth part of the time rust and decay 
would have destroyed it had it lain on the earth, but in 
the solitudes of space there was found no air or damp 
to produce corrosion. At last, after the completion of 
its long travels, it again crashed down on the earth. 

We have now briefly surveyed the extent of the solar 



A REVIEW. 317 

system. We began with the sun, which presides over 
all, and then we discussed the various planets with their 
satellites, next we considered the eccentric comets, and 
finally the minute bodies which, as shooting stars or 
meteorites, must be regarded as forming part of the 
Sun's system. In our closing lecture we shall have to 
deal with objects of a far more magnificent character. 



LECTURE VI. 

STARS. 

We try to make a Map — The Stars are Suns — The Numbers of the Stars 

— The Clusters of Stars — The Rank of the Earth as a Globe in Space 

— The Distances of the Stars — The Brightness and Color of Stars — 
Double Stars — How we find what the Stars are made of — The 
Nebula 1 — What the Nebula? are made of — Photographing the Nebulae 

— Conclusion. 

AVE TRY TO MAKE A MAP. 

The group of bodies which cluster around our sun 
forms a little island, so to speak, in the extent of infinite 
space. We may illustrate this by a map in which Ave 
shall endeavor to show the stars placed at their proper 
relative distances. We first open the compasses one 
inch, and thus draw a little circle to represent the path 
of the earth. We are not going to put in all the planets. 
We take Neptune, the outermost, at once. To draw its 
path I open the compasses to thirty inches, and draw a 
circle with that radius. That will do for our solar sys- 
tem, though the comets no doubt will roam beyond 
these limits. To complete our map Ave ought of course 
to put in some stars. There are a hundred million to 
choose from, and Ave shall begin with the brightest. It 
is often called the Dog Star, but astronomers know it 
better as Sirius. Let us see where it is to be placed 
on our map. Sirius is beyond Neptune, so it must be 
outside someAvhere, Indeed, it is a good deal further 

318 



MAKING A MAP. 319 

off than Neptune ; so I try at the edge of the drawing- 
board ; I have got a method of making a little calcula- 
tion that I do not intend to trouble you with, but I 
can assure you that the results it leads me to are 
quite correct; they show me that this board is not 
big enough. But could a board which was big enough 
fit into this lecture theatre ? Here, again, I make my 
little calculations, and I find that there would not be 
room for a board sufficiently great ; in fact, if I put the 
sun here at one end, with its planets around it, Sirius 
would be too near on the same scale if it were at 
the further corner. The board would have to go out 
through the wall of the theatre, out through London. 
Indeed, bio- as London is, it would not be large enough 
to contain the drawing-board that I should require. It 
would have to stretch about twenty miles from where 
we are now assembled. We may therefore dismiss any 
hope of making a practical map of our system on this 
scale if Sirius is to have its proper place. Let us, then, 
take some other star. We shall naturally try with the 
nearest of all. It is one that we do not know in this 
part of the world, but those that live in the southern 
hemisphere are well acquainted with it. The name of 
this star is Alpha Centauri. Even for this star, we 
should require a drawing three or four miles long if 
the distance from the earth to the sun is to be taken as 
one inch. You see what an isolated position our sun 
and his planets occupy. The members of the family 
are all close together, and the nearest neighbors are 
situated at enormous distances. There is a good reason 
for this separation. The stars are very pretty and 



320 STAR-LAND. 

perfectly harmless to us where they are at present 
situated. They might be very troublesome neighbors 
if they were very much closer to our system. It is 
therefore well they are so far off ; they would be con- 
stantly making disturbance in the sun's family if they 
were near at hand. Sometimes they would be dragging 
us into unpleasantly great heat by bringing us too close 
to the sun, or producing a coolness by pulling us away 
from the sun, which would be quite as disagreeable. 

THE STARS ARE SUNS. 

We are about to discuss one of the grandest truths 
in the whole of nature. We have had occasion to see 
that this sun of ours is a magnificent globe immensely 
larger than the greatest of his planets, while the greatest 
of these planets is immensely larger than this earth; 
but now we are to learn that our sun is, indeed, only a 
star not nearly so bright as many of those which shine 
over our heads every night. We are comparatively 
close to the sun, so that we are able to enjoy his 
beautiful light and cheering heat. Each of those other 
myriads of stars is a sun, and the splendor of those 
distant suns is often far greater than that of our own. 
We are, however, so enormously far from them that 
they appear dwindled down to insignificance. To judge 
impartially between our sun or star and such a sun or 
star as Sirius we should stand halfway between the 
two ; it is impossible to make a fair estimate when we 
find ourselves situated close to one star and a million 
times as far from the other. After allowance is made 



HOW MANY STARS ARE THERE? 321 

for the imperfections of our point of view, we are 
enabled to realize the majestic truth that the sun is 
no more than a star, and that the other stars are no 
less than suns. This gives us an imposing idea of the 
extent and the magnificence of the universe in which 
we are situated. Look up at the sky at night — you 
will see a host of stars ; try to think that every one of 
them is itself a sun. It may probably be that those 
suns have planets circulating round them, but it is 
hopeless for us to expect to see such planets. Were 
you standing on one of those stars and looking towards 
our system, you would not perceive the sun to be the 
brilliant and gorgeous object that we knew so well. If 
you could see him at all, he would merely seem like a 
star, not nearly so bright as many of those you can see 
at night. Even if you had the biggest of telescopes to 
aid your vision, you could never discern from one of 
these bodies the planets which surround the sun. No 
astronomer in the stars could see Jupiter even if his 
sight were a thousand times as good or his telescopes a 
thousand times as powerful as any sight or telescope 
that we know. So minute an object as our earth would, 
of course, be still more hopelessly beyond the possibility 
of vision. 

THE NUMBERS OF THE STARS. 

To count the stars involves a task which lies beyond 
the power of man to accomplish. Even without the 
aid of any telescope, we can see a great multitude of 
stars from this part of the world. There are also many 



322 STAR-LAND. 

constellations in the southern hemisphere which never 
appear above our horizon. If, however, we were to go 
to the equator, then, by waiting there for a twelve- 
month, all the stars in the heavens would have been 
successively exposed to view. An astronomer, Houzeau, 
with the patience to count them, enumerated about 
6000. This is the naked-eye estimate of the star- 



D 


if 
\ . 
\' 
\ 
\ 

i 

1 
1 

A 






m 

H 
rn 


r \ 

V \ 


The Little Bear 




> 

30 


O n 


.The Pole 










The Pole Star 

• — 


i 

i 



Fig. 82. — The Great Bear and the Pole. 

population of the heavens; but if, instead of relying 
on unaided vision, you get the assistance of a little 
telescope, you will be astounded at the enormous multi- 
tude of stars which are disclosed. 

An ordinary opera-glass or binocular is a very useful 
instrument for looking at the stars in the heavens. If 
you employ an instrument of this sort, you will be 
amazed to find that the heavens teem with additional 



COUNTING THE STARS. 323 

hosts of stars that your unaided vision would never have 
given you knowledge of. Any part of the sky may 
be observed ; but, just to give an illustration, I shall 
take one special region, namely, that of the Great Bear 
(Fig. 82). The seven well-known stars are here shown, 
four of which form a sort of oblong, while the other 
three represent the tail. I would like you to make this 
little experiment. On a fine clear night, count how 
many stars there are within this oblong ; they are all 
very faint, but you will be able to see a few, and, with 
good sight, and on a clear night, you may see perhaps 
ten. Next take your opera-glass and sweep it over 
the same region ; if you will carefully count the stars 
it shows, you will find fully 200 ; so that the opera- 
glass has, in this part of the sky, revealed nearly twenty 
times as many stars as could be seen without its aid. 
As 6000 stars can be seen by the eye all over the 
heavens, we may fairly expect that twenty times that 
number — that is to say, 120,000 stars — could be 
shown by the opera-glass over the entire sky. Let us 
go a step further, and employ a telescope, the object- 
glass of which is three inches across. This is a useful 
telescope to have, and, if a good one, will show multi- 
tudes of pleasing objects, though an astronomer would 
not consider it very powerful. An instrument like 
this, small enough to be carried in the hand, has been 
applied to the task of enumerating the stars in the 
northern half of the sky, and 320,000 stars were 
counted. Indeed, the actual number that might have 
been seen with it is considerably greater, for when the 
astronomer Argelander made this memorable investiga- 



324 STAR-LAND. 

tion he was unable to reckon many of the stars in 
localities where they lay very close together. This 
grand count only extended to half the sky, and, assum- 
ing that the other half is as richly inlaid with stars, we 
see that a little telescope like that we have supposed 
will, when swept over the heavens, reveal a number of 
stars which exceeds that of the population of any city 
in England except London. It exhibits more than one 
hundred times as many stars as our eyes could possibly 
reveal. Still, we are only at the beginning of the 
count; the very great telescopes add largely to the 
number. There are multitudes of stars which in small 
instruments we cannot see, but which are distinctly 
visible from our great observatories. That telescope 
would be still but a comparatively small one which 
would show as many stars in the sky as there are 
people living in this mighty city of London ; and with 
the greatest instruments, the tale of stars has risen to 
a number far greater than that of the entire population 
of Great Britain. 

In addition to those stars which the largest telescopes 
show us, there are myriads which make their presence 
evident in a wholly different way. It is only in quite 
recent times that an attempt has been made to develop 
fully the powers of photography in representing the 
celestial objects. On a photographic plate which has 
been exposed to the sky in a great telescope the stars 
are recorded by thousands. Many of these may, of 
course, be observed with a good telescope, but there 
are not a few others which no one ever saw in a tele- 
scope, which apparently no one ever could see, though 



PHOTOGRAPHING THE STARS. 325 

the photograph is able to show them. We do not, how- 
ever, employ a camera like that which the photographer 
uses who is going to take your portrait. The astron- 
omer's plate is put into his telescope, and then the tele- 
scope is turned towards the sky. On that plate the 
stars produce their images, each by its own light. Some 
of these images are excessively faint, but we give a very 
long exposure of an hour or two hours ; sometimes as 
much as four hours' exposure is given to a plate so sen- 
sitive that a mere fraction of a second would sufficiently 
expose it during the ordinary practice of taking a pho- 
tograph in daylight. We thus afford sufficient time 
to enable the fainter objects to indicate their presence 
upon the sensitive film. Even with an exposure of a 
single hour a picture exhibiting 16,000 stars has been 
taken by Mr. Isaac Roberts, of Liverpool. Yet the 
portion of the sky which it represents is only one ten- 
thousandth part of the entire heavens. It should be added 
that the region which Mr. Roberts has photographed is 
furnished with stars in rather exceptional profusion. 

Here, at last, we have obtained some conception of 
the sublime scale on which the stellar universe is con- 
structed. Yet even these plates cannot represent all 
the stars that the heavens contain. We have every 
reason for knowing that with larger telescopes, wi£h 
more sensitive plates, with more prolonged exposures, 
ever fresh myriads of stars will be brought within our 
view. 

You must remember that every one of these stars is 
truly a sun, a lamp, as it were, which doubtless gives 
light to other objects in its neighborhood as our sun 



326 STAR-LAND. 

sheds light upon this earth and the other planets. In 
fact, to realize the glories of the heavens you should 
try to think that the brilliant points you see are merely 
the luminous points of the otherwise invisible universe. 

Standing one fine night on the deck of a Cunarder 
we passed in open ocean another great Atlantic steamer. 
The vessel was near enough for us to see not only the 
light from the mast-head but also the little beams from 
the several cabin ports ; and we could see nothing of 
the ship herself. Her very existence was only known 
to us by the twinkle of these lights. Doubtless her 
passengers could see, and did see, the similar lights 
from our own vessel, and they probably drew the 
correct inference that these lights indicated a great 
ship. 

Consider the multiplicity of beings and objects in 
a ship : the captain and the crew, the passengers, the 
cabins, the engines, the boats, the rigging, and the 
stores. Think of all the varied interests there collected 
and then reflect that out on the ocean, at night, the 
sole indication of the existence of this elaborate struc- 
ture was given by the few beams of light that happened 
to radiate from it. Now raise your eyes to the stars ; 
there are the twinkling lights. We cannot see what 
those lights illuminate, we can only conjecture what 
untold wealth of non-luminous bodies may also lie in 
their vicinity ; we may, however, feel certain that just as 
the few gleaming lights from a ship are utterly inade- 
quate to give a notion of the nature and the contents 
of an Atlantic steamer, so are the twinkling stars utterly 
inadequate to give even the faintest conception of the 



STAR CLUSTERS. 327 

extent and the interest of the universe. We merely 
see self-luminous bodies, but of the multitudes of objects 
and the elaborate systems of which these bodies are only 
the conspicuous points we see nothing and we know 
very little. We are, however, entitled to infer from an 
examination of our own star — the sun — and of the 
beautiful system by which it is surrounded, that these 
other suns may be also splendidly attended. This is 
quite as reasonable a supposition as that a set of lights 
seen at night on the Atlantic Ocean indicates the exist- 
ence of a fine ship. 

THE CLUSTERS OF STARS. 

On a clear night you can often see, stretching across 
the sky, a track of faint light, which is known to astron- 
omers as the " Milky Way." It extends below the hori- 
zon and then round the earth to form a girdle about the 
heavens. When we examine the Milky Way with a tele- 
scope we find, to our amazement, that it consists of 
myriads of stars, so small and so faint that we are not 
able to distinguish them individually ; Ave merely see 
the glow produced from their collective rays. Remem- 
bering that our sun is a star, and that the Milky Way 
surrounds us, it would almost seem as if our sun were 
but one of the host of stars which form this cluster. 

There are also other clusters of stars, some of which 
are exquisitely beautiful telescopic spectacles. I may 
mention a celebrated pair of these objects which lies in 
the constellation of Perseus. The sight of them in a 
great telescope is so imposing that no one who is fit to 



328 STAR-LAND. 

look through a telescope could resist a shout of wonder 
and admiration when first they burst on his view. But 
there are other clusters. Here is a picture of one 
which is known as the " Globular Cluster in the Cen- 
taur" (Fig. 83). It consists of a ball of stars, so far 
off that, however large these several suns may actually 




Fig. 83. — Globular Cluster iu the Centaur. 

be, they have dwindled down to extremely small points 
of light. A homely illustration may serve to show the 
appearance which a globular cluster presents in a good 
telescope. I take a pepper-castor and on a sheet of 
white paper I begin to shake out the pepper until there 
is a little heap at the centre and other grains are scat- 
tered loosely about. Imagine that every one of those 
grains of pepper was to be transformed into a tiny elec- 
tric light, and then you have some idea of what a cluster 
of stars would look like when viewed through a telescope 
of sufficient power. There are multitudes of such 



MR. JOHN SMITH. 329 

groups scattered through the depths of space. They 
require our biggest telescopes to show them adequately. 
We have seen that our sun is a star, being only one of 
a magnificent cluster that form the Milky Way. We 
have also seen that there are other groups scattered 
through the length and depth of space. It is thus we 
obtain a notion of the rank which our earth holds in 
the scheme of things celestial. 

THE RANK OF THE EARTH AS A GLOBE IN SPACE. 

Let me give an illustration with the view of explain- 
ing more fully the nature of the relation which the 
earth bears to the other globes which abound through 
space, and you must allow me to draw a little upon my 
imagination. I shall suppose that Her Majesty's mails 
extend not only over this globe, but that they also com- 
municate with other worlds ; that postal arrangements 
exist between Mars and the earth, between the sun and 
Orion — in fact, everywhere throughout the whole ex- 
tent of the universe. We shall consider how our letters 
are to be addressed. Let us take the case of Mr. John 
Smith, merchant, who lives at 1001, Piccadilly; and 
let us suppose that Mr. John Smith's business trans- 
actions are of such an extensive nature that they reach 
not only all over this globe, but away throughout space. 
I shall suppose that the firm has a correspondent resid- 
ing — let us say in the constellation of the Great Bear; 
and when this man of business wants to write to Mr. 
Smith from these remote regions, what address must he 
put upon the letter, so that the Postmaster-General of 



330 STAK-LANB. 

the universe shall make no mistake about its delivery ? 
He will write as follows : — 

Mr. John Smith, 
1001 Piccadilly, 
London, 

England, 
Europe, 
Earth, 

Near the Sun, 
Milky Way, 

The Universe. 

Let us now see what the several lines of this address 
mean. Of course we put down the name of Mr. John 
Smith in the first line, and then we will add "1001 
Piccadilly" for the second; but as the people in the 
Great Bear are not likely to know where Piccadilly is, 
we shall add " London " underneath. As even London 
itself cannot be well known everywhere, it is better to 
write "England." This would surely find Mr. John 
Smith from any post-office on this globe. From other 
globes, however, the supreme importance of England 
may not be so immediately recognized, and therefore it 
is as well to add another line, " Europe." This ought 
to be sufficient, I think, for any post-office in the solar 
system. Europe is big enough to be visible from Mars 
or Venus, and should be known to the post-office people 
there, just as we know and have names for the conti- 
nents on Mars. But further away there might be a 
little difficulty ; from Uranus and Neptune the different 
regions on our earth can never have been distinguished, 
and therefore we must add another line to indicate the 
particular globe of the solar system which contains 



DIFFICULTIES OF ADDRESS. 331 

Europe. Mark Twain tells us that there was always 
one thing in astronomy which specially puzzled him, 
and that was to know how we found out the names of 
the stars. We are, of course, in hopeless ignorance of 
the name by which this earth is called among other 
intelligent beings elsew T here w T ho can see it. I can 
only adopt the title of " Earth," and therefore I add 
this line. Now our address is so complete that from 
anywhere in the solar system — from Mercury, from 
Jupiter, or Neptune — there ought to be no mistake 
about the letter finding its way to Mr. John Smith. 
But from his correspondent in the Great Bear this 
address would be still incomplete ; they cannot see our 
earth from there, and even the sun himself only looks 
like a small star — like one, in fact, of thousands of stars 
elsewhere. However, each star can be distinguished, 
and our sun may, for instance, be recognized from the 
Great Bear by some designation. We shall add the 
line " Near the Sun," and then I think that from this 
constellation, or from any of the other stars around us, 
the address of Mr. John Smith may be regarded as com- 
plete. But Mr. Smith's correspondence may be still 
wider. He may have an agent living in the cluster of 
Perseus or on some other objects still fainter and more 
distant; then " Near the Sun" is utterly inadequate 
as a concluding line to the address, for the sun, if it 
can be seen at all from thence, will be only of the sig- 
nificance of an excessively minute star, no more to be 
designated by a special name than are each of the several 
leaves on the trees of a forest. What this distant cor- 
respondent will be acquainted with is not the earth or the 



332 STAR-LAND. 

sun, but only the cluster of stars among which the sun 
is but a unit. Again we use our own name to denote 
the cluster, and we call it the " Milky Way." When 
we add this line, we have made the address of Mr. John 
Smith as complete as circumstances will permit. I think 
a letter posted to him anywhere ought to reach its des- 
tination. To perfect it, however, we will finish up with 
one line more — " The Universe." 

THE DISTANCES OF THE STARS. 

I must now tell you something about the distances 
of the stars. I shall not make the attempt to explain 
fully how astronomers make such measurements, but I 
will give you some notion of how it is done. You may 
remember I showed you how Ave found the distance of 
a globe that was hung from the ceiling. The principle 
of the method for finding the distance of a star is some- 
what similar, except that we make the two observations 
not from the two ends of a table, not even from opposite 
sides of the earth, but from two opposite points on the 
earth's orbit, which are therefore at a distance of 186,- 
000,000 miles. Imagine that on Midsummer Day, when 
standing on the earth here, I measure with a piece of card 
the angle between the star and the sun. Six months 
later, on Midwinter Day, when the earth is at the oppo- 
site point of its orbit, I again measure the angle between 
the same star and the sun, and we can now determine 
the star's distance by making a triangle. I draw a line 
a foot long, and we will take this foot to represent 186,- 
000,000 miles, the distance between the two stations ; 



MEASURING THE DISTANCES OF THE STARS. 333 

then placing the cards at the corners, I rule the two 
sides and complete the triangle, and the star must be 
at the remaining corner; then I measure the sides of 
the triangle, and find how many feet they contain, and 
recollecting that each foot corresponds to 186,000,000 
miles, we discover the distance of the star. If the 
stars were comparatively near us, the process would be 
a very simple one ; but, unfortunately, the stars are so 
extremely far off that this triangle, even with a base 
of only one foot, must have its sides many miles long. 
Indeed, astronomers will tell you that there is no more 
delicate or troublesome work in the whole of their sci- 
ence than that of discovering the distance of a star. 

In all such measurements we take the distance from 
the earth to the sun as a conveniently long measuring- 
rod, whereby to express the results. The nearest stars 
are still hundreds of thousands of times as far off as the 
sun. Let us ponder for a little on the vastness of these 
distances. We shall first express them in miles. Tak- 
ing the sun's distance to be 93,000,000 miles, then the 
distance of the nearest fixed star is about twenty mil- 
lions of millions of miles — that is to say, we express 
this by putting down a 2 first, and then writing thir- 
teen ciphers after it. It is, no doubt, easy to speak of 
such figures, but it is a very different matter when we 
endeavor to imagine the awful magnitude which such a 
number indicates. I must try to give some illustrations 
which will enable you to form a notion of it. At first 
I was going to ask you to try and count this number, 
but when I found it would require at least 300,000 
years, counting day and night without stopping, before 



334 STAR-LAND. 

the task was over, it became necessary to adopt some 
other method. 

When on a visit in Lancashire I was once kindly 
permitted to visit a cotton mill, and I learned that the 
cotton yarn there produced in a single day would be long 
enough to wind round this earth twenty-seven times at 
the equator. It appears that the total production of 
cotton yarn each day in all the mills together would 
be on the average about 155,000,000 miles. In fact, 
if they would only spin about one-fifth more, we could 
assert that Great Britain produced enough cotton yarn 
every day to stretch from the earth to the sun and back 
again ! It is not hard to find from these figures how 
long it would take for all the mills in Lancashire to 
produce a piece of yarn long enough to reach from our 
earth to the nearest of the stars. If the spinners worked 
as hard as ever they could for a year, and if all the 
pieces were then tied together, they would extend to 
only a small fraction of the distance ; nor if they worked 
for ten years, or for twenty years, would the task be fully 
accomplished. Indeed, upwards of 400 years would be 
necessary before enough cotton could be grown in 
America and spun in this country to stretch over a 
distance so enormous. All the spinning that has ever 
yet been done in the world has not formed a long enough 
thread ! 

There is another way in which we can form some 
notion of the immensity of these sidereal distances. 
You will recollect that, when we were speaking of 
Jupiter's moons (p. 219), I told you of the beautiful 
discovery which their eclipses enabled astronomers to 



WHAT WE REALLY SEE. 335 

make. It was thus found that light travels at the enor- 
mous speed of about 185,000 miles per second. It moves 
so quickly that within a single second a ray would flash 
two hundred times from London to Edinburgh and back 
again. 

We said that a meteor travels one hundred times as 
swiftly as a rifle-bullet; but even this great speed seems 
almost nothing when compared with the speed of light, 
which is 10,000 times as great. Suppose some brilliant 
outbreak of light were to take place in a distant star — 
an outbreak which would be of such intensity that the 
flash from it would extend far and wide throughout the 
universe. The light would start forth on its voyage 
with terrific speed. Any neighboring star which was at 
a distance of less than 185,000 miles would, of course, 
see the flash within a second after it had been produced. 
More distant bodies would receive the intimation after 
intervals of time proportional to their distances. Thus, 
if a body were 1,000,000 miles away the light would 
reach it in from five to six seconds, while over a distance 
as great as that which separates the earth from the sun 
the news would be carried in about eight minutes. We 
can calculate how long a time must elapse ere the light 
shall travel over a distance so great as that between the 
star and our earth. You will find that from the near- 
est of the stars the time required for the journey will 
be over three years. Ponder on all that this involves. 
That outbreak in the star might be great enough to be 
visible here, but we could never become aware of it till 
three years after it had happened. When we are look- 
ing at such a star to-night we do not see it as it is at 



336 STAR-LAND. 

present, for the light that is at this moment entering 
our eyes has travelled so far that it has been three years 
on the way. Therefore, when we look at the star now 
we see it as it was three years previously. In fact, if 
the star were to go out altogether, we might still con- 
tinue to see it twinkling for a period of three years 
longer, because a certain amount of light was on its way 
to us at the moment of extinction, and so long as that 
light keeps arriving here, so long shall we see the star 
showing as brightly as ever. When, therefore, you look 
at the thousands of stars in the sky to-night, there is 
not one that you see as it is now, but as it was years 
ago. 

I have been speaking of the stars that are nearest to 
us, but there are others much farther off. It is true 
we cannot find the distance of these more remote 
objects with any degree of accuracy, but we can con- 
vince ourselves how great that distance is by the fol- 
lowing reasoning. Look at one of the brightest stars. 
Try to conceive that the object was carried away 
further into the depths of space, until it was ten times 
as far from us as it is at present, it would still remain 
bright enough to be recognized in quite a small tele- 
scope ; even if it were taken to one hundred times its 
original distance it would not have withdrawn from the 
view of a good telescope ; while if it retreated one 
thousand times as far as it was at first it would still 
be a recognizable point in our mightiest instruments. 
Among the stars which we can see with our telescopes, 
we feel confident there must be many from which the 
light has expended hundreds of years, or even thousands 



SEEING ANCIENT HISTORY. 337 

of years, on the journey. When, therefore, we look at 
such objects, we see them, not as they are now, but as 
they were ages ago ; in fact, a star might have ceased 
to exist for thousands of years, and still be seen by us 
every night as a twinkling point in our great telescopes. 
Remembering these facts, you will, I think, look at 
the heavens with a new interest. There is a bright 
star, Vega or Alpha Lyrse, a beautiful gem, so far off 
that the light from it which now reaches our eyes 
started before many of my audience were born. Sup- 
pose that there are astronomers residing on worlds amid 
the stars, and that they have sufficiently powerful 
telescopes to view this globe, what do you think they 
would observe ? They will not see our earth as it is at 
present, they will see it as it was years, and sometimes 
many years, ago. There are stars from which, if 
England could now be seen, the whole of the country 
would be observed at this present moment to be in a 
great state of excitement at a very auspicious event. 
Distant astronomers might notice a great procession in 
London, and they could watch the coronation of a 
youthful queen amid the enthusiasm of a nation. 
There are other stars still further, from which, if the 
inhabitants had good enough telescopes, they would 
now see a mighty battle in progress not far from 
Brussels. One splendid army could be beheld hurling 
itself time after time against the immovable ranks of 
the other. They would not, indeed, be able to hear 
the ever-memorable, " Up, Guards, and at them ! " but 
there can be no doubt that there are stars so far away 
that the rays of light which started from the earth on 



338 STAR-LAND. 

the day of the battle of Waterloo are only just arriving 
there. Further off still, there are stars from which a 
bird's-eye view could be taken at this very moment of 
the signing of Magna Charta, There are even stars 
from which England, if it could be seen at all, would 
now appear, not as the great England we know, but as 
a country covered by dense forests, and inhabited by 
painted savages, who waged incessant war with wild 
beasts that roamed through the island. The geological 
problems that now puzzle us would be quickly solved 
could Ave only go far enough into space and had wc 
only powerful enough telescopes. We should then be 
able to view our earth through the successive epochs 
of past geological time ; we should be actually able to 
see those great animals Avhose fossil remains are treas- 
ured in our museums tramping about over the earth's 
surface, splashing across its swamps, or swimming with 
broad flippers through its oceans. Indeed, if we could 
view our own earth reflected from mirrors in the stars, 
we might still see Moses crossing the lied Sea, or Adam 
and Eve being expelled from Eden. 

So important is the subject of star distance that I am 
tempted to give one more illustration in order to bring 
before you some conception of how vast such distances 
are. I shall take, as before, the nearest of the stars so 
far as known to us, and I hope to be forgiven for taking 
an illustration of a practical and a commercial kind 
instead of one more purely scientific. I shall suppose 
that a railway is about to be made from London to 
Alpha Centauri. The length of that railway, of course, 
we have already stated : it is twenty billions of miles. 



AN EXPENSIVE TICKET. 339 

So I am now going to ask your attention to the simple 
question as to the fare which it Avould be reasonable to 
charge for the journey. We shall choose a very cheap 
scale on which to compute the price of a ticket. The 
parliamentary rate here is, I believe, a penny for every 
mile. We will make our interstellar railway fares 
much less even than this; we shall arrange to travel at 
the rate of one hundred miles for every penny. That, 
surely, is moderate enough. If the charges were so 
low that the journey from London to Edinburgh only 
cost fourpence, then even the most unreasonable pas- 
senger would be surely contented. On these terms how 
much do you think the fare from London to this star 
ought to be? I know of one way in which to make 
our answer intelligible. There is a National Debt with 
which your fathers are, unhappily, only too well ac- 
quainted ; you will know quite enough about it your- 
selves in those days when you have to pay income tax. 
This debt is so vast that the interest upon it is about 
sixty thousand pounds a day, the whole amount of the 
National Debt being six hundred and thirty-eight 
millions of pounds (April, 1898). 

If you went to the booking office with the whole of 
this mighty sum in your pocket — but stop a moment ; 
could you carry it in your pocket? Certainly not, if 
it were in sovereigns. You would find that after you 
had as many sovereigns as you could conveniently carry 
there would still be some left — so many, indeed, that 
it would be necessary to get a cart to help you on with 
the rest. When the cart had as great a load of sover- 
eigns as the horse could draw there would be still some 



340 STAR-LAND. 

more, and you would have to get another cart ; but ten 
carts, twenty carts, fifty carts, would not be enough. 
You would want five thousand of these before you 
would be able to move off towards the station with your 
money. When you did get there and asked for a ticket 
at the rate of one hundred miles for a penny, do you 
think you would get any change ? No doubt some 
little time would be required to count the money, but 
when it was counted the clerk would tell you that there 
was not enough, that he must have nearly two hundred 
millions of pounds more. 

That will give some notion of the distance of the 
nearest star, and we may multiply it by ten, by one 
hundred, and even by one thousand, and still not attain 
to the distance of some of the more remote stars that 
the telescope shows us. 

On account of the immense distances of the stars we 
can only perceive them to be mere points of light. We 
can never see a star to be a globe with marks on it like 
the moon, or like one of the planets — in fact, the bet- 
ter the telescope the smaller does the star seem, though, 
of course, its brightness is increased with every addition 
to the light-grasping power of the instrument. 

THE BRIGHTNESS AND COLOR OF STARS. 

Another point to be noticed is the arrangement of 
stars in classes, according to their lustre. The brightest 
stars, of which there are about twenty, are said to be 
of the first magnitude. Those just inferior to the first 
magnitude are ranked as the second ; and those just 



COLORED STARS. 341 

lower than the second are estimated as the third ; and 
so on. The smallest points that your unaided eyes will 
show you are of about the sixth magnitude. Then the 
telescope will reveal stars still fainter and fainter, down 
to what we term the seventeenth or eighteenth magni- 
tudes, or even lower still. The number of stars of each 
magnitude increases very much in the classes of small 
ones. 

Most of the stars are white, but many are of a some- 
what ruddy hue. There are a few telescopic points 
which are intensely red, some exhibit beautiful golden 
tints, while others are blue or green. 

There are some curious stars which regularly change 
their brilliancy. Let me try to illustrate the nature of 
these variables. Suppose that you were looking at a 
street gas-lamp from a very long distance, so that it 
seemed a little twinkling light ; and suppose that some 
one was preparing to turn the gas-cock up and down. 
Or, better still, imagine a little machine which would 
act regularly so as to keep the light first of all at its 
full brightness for two days and a half, and then gradu- 
ally turn it down until in three or four hours it declines 
to a feeble glimmer. In this low state the light remains 
for twenty minutes ; then during three or four hours 
the gas is to be slowly turned on again until it is full. 
In this condition the light will remain for two days and 
a half, and then the same series of changes is to recom- 
mence. This would be a very odd form of gas-lamp. 
There would be periods of two days and a half during 
which it would remain at its full ; these would be sep- 
arated by intervals of about seven hours, when the 



342 STAR-LAND. 

gradual turning down and turning up again would be in 
progress. 

The imaginary gas-lamp is exactly paralleled by a 
star Algol, in the constellation of Perseus (Fig. 84), 
which goes through the series of changes I have 
indicated. Ordinarily speaking, it is a bright star of 
the second magnitude, and, whatever be the cause, the 
star performs its variations with marvellous uniformity. 
In fact, Algol has always arrested the attention of those 
who observed the heavens, and in early times was 
looked on as the eye of a Demon. There are many 
other stars which also change their brilliancy. Most of 
them require much longer periods than Algol, and 
sometimes a new star which nobody has ever seen before 
will suddenly kindle into brilliancy. It is now known 
that the bright star Algol is attended by a dark com- 
panion. This dark star sometimes comes between Algol 
and the observer and cuts off the light. Thus it is that 
the diminution of brightness is produced. 

DOUBLE STARS. 

Whenever you have a chance of looking at the 
heavens through a telescope, you should ask to be shown 
what is called a double star. There are many stars in 
the heavens which present no remarkable appearance to 
the unaided eye, but which a good telescope at once 
shows to be of quite a complex nature. These are 
what we call double stars, in which two quite distinct 
stars are placed so close together that the unaided eye 
is unable to separate them. Under the magnifying 



A DOUBLE STAR. 



343 



power of the telescope, however, they are seen to be 
distinct. In order to give some notion of what these 
objects are like, I shall briefly describe three of them. 



• 
Cassiopeia ■ 


- 




/•V: Glorious 
Star Cluster 




rt 






Perseus^a 






• 1 : 53 1 : "'■' P ""'-'. 


Vc 






Capella^ 

1st. Mag* """ 

% The Kids 




• Algol 
Wonderfu 


the 

1 Variable 


AURIGA 


\ 

\ 






■ 

• 

j 


H 


••V.'The PI 


eiades 


THE BULL 








• 

Aldebaran^ ; 
1st. Mag 


The Hyades ' 













Fig. 84. — Perseus and its Neighboring Stars, including Algol. 



The first lies in that best known of constellations, the 
Great Bear. If you look at his tail, which consists of 
three stars, you will see that near the middle one of the 
three a small star is situated ; we call this little star 
Alcor, but it is the brighter one near Alcor to which I 



344 STAR-LAND. 

specially call your attention. The sharpest eye would 
never suspect that it was composed of two stars placed 
close together. Even a small telescope will, however, 
show this to be the case, and this is the easiest and the 
first observation that a young astronomer should make 
when beginning to turn a telescope to the heavens. 
Of course, you will not imagine that I mean Alcor to be 
the second component of the double star ; it is the 
bright star near Alcor which is the double. Here are 
two marbles, and these marbles are fastened an inch 
apart. You can see them, of course, to be separate ; 
but if the pair were moved further and further away, 
then you would soon not be able to distinguish between 
them, though the actual distance between the marbles 
had not altered. Look at these two wax tapers which 
are now lighted ; the little flames are an inch apart. 
You would have to view them from a station a third of 
a mile away if the distance between the two flames 
were to appear the same as that between the two com- 
ponents of this double star. Your eye would never be 
able to discriminate between two lights only an inch 
apart at so great a distance ; a telescope would, how- 
ever, enable you to do so, and this is the reason why 
we have to use telescopes to show us double stars. 

You might look at that double star year after year 
throughout the course of a long life without finding 
any appreciable change in the relative positions of its 
components. But we know that there is no such thing 
as rest in the universe; even if you could balance a 
body so as to leave it for a moment at rest, it would 
not stay there, for the simple reason that all the bodies 



CASTOR AND POLLUX. 345 

round it in every direction are pulling at it, and it is 
certain that the pull in one direction will preponderate, 
so that move it must. Especially is this true in the 
case of two suns like those forming a double star. 
Placed comparatively near each other they could not 
remain permanently in that position ; they must gradu- 
ally draw together and come into collision with an awful 
crash. There is only one way by which such a disaster 
could be averted. That is by making one of these 
stars revolve around the other just as the earth revolves 
around the sun, or the moon revolves around the earth. 
Some motion must, therefore, be going on in every gen- 
uine double star, whether we have been able to see that 
motion or not. 

Let us now look at another double star of a different 
kind. This time it is in the constellation of Gemini. 
The heavenly twins are called Castor and Pollux. Of 
these, Castor is a very beautiful double star, consisting of 
two bright points, a great deal closer together than were 
those in the Great Bear ; consequently a better telescope 
is required for the purpose of showing them separately. 
Castor has been watched for many years, and it can be 
seen that one of these stars is slowly revolving around 
the other ; but it takes a very long time, amounting to 
hundreds of years, for a complete circuit to be accom- 
plished. This seems very astonishing, but when you 
remember how exceedingly far Castor is, you will per- 
ceive that that pair of stars which appear so close 
together that it requires a telescope to show them 
apart must indeed be separated by hundreds of mil- 
lions of miles. Let us try to conceive our own system 



346 STAR-LAND. 

transformed into a double star. If we took our outer- 
most planet — Neptune — and enlarged him a good 
deal, and then heated him sufficiently to make him 
glow like a sun, he would still continue to revolve 
round our sun at the same distance, and thus a double 
star would be produced. An inhabitant of Castor who 
turned his telescope towards us would be able to see 
the sun as a star. He would not, of course, be able to 
see the earth, but he might see Neptune like another 
small star close to the sun. If generations of astron- 
omers in Castor continued their observations of our 
system, they would find a binary star, of which one 
component took a century and a half to go round the 
other. Need we then be surprised that when we look 
at Castor we observe movements that seem very slow ? 
There is often so much diffused light about the bright 
stars seen in a telescope, and so much twinkling in 
some states of the atmosphere, that stars appear to 
dance about in rather a puzzling fashion, especially to 
one who is not accustomed to astronomical observations. 
I remember hearing how a gentleman once came to 
visit an observatory. The astronomer showed him 
Castor through a powerful telescope as a fine specimen 
of a double star, and then, by way of improving his 
little lesson, the astronomer mentioned that one of 
these stars was revolving around the other. " Oh, 
yes," said the visitor, " I saw them going round and 
round in the telescope." He would, however, have 
had to wait for a few centuries with his eye to the 
instrument before he would have been entitled to make 
this assertion. 



WHAT ARE THE STARS MADE OF? 347 

Double stars also frequently delight us by giving 
beautifully contrasted colors. I dare say you have 
often noticed the red and the green lights that are 
used on railways in the signal lamps. Imagine one of 
those red and one of those green lights away far up in 
the sky and placed close together, then you would have 
some idea of the appearance that a colored double star 
presents, though, perhaps, I should add that the hues 
in the heavenly bodies are not so vividly different as 
are those which our railway people find necessary. 
There is a particularly beautiful double star of this 
kind in the constellation of the Swan. You could 
make an imitation of it by boring two holes, with a 
red-hot needle, in a piece of card, and then covering 
one of these holes with a small bit of the topaz-colored 
gelatine with which Christmas crackers are made. The 
other star is to be similarly colored with blue gelatine. 
A slide made on this principle placed in the lantern 
gives a very good representation of these two stars on 
the screen. There are many other colored doubles 
besides this one ; and, indeed, it is noteworthy that we 
hardly ever find a blue or a green star by itself in the 
sky ; it is always as a member of one of these pairs. 

HOW WE FIND WHAT THE STARS ARE MADE OF. 

Here is a piece of stone. If I wanted to know what 
it was composed of, I should ask a chemist to tell me. 
He would take it into his laboratory, and first crush it 
into powder, and then, with his test tubes, and with 
the liquids which his bottles contain, and his weighing 



348 STAR-LAND. 

scales, and other apparatus, he will tell all about it ; there 
is so much of this, and so much of that, and plenty of this, 
and none at all of that. But now, suppose you ask this 
chemist to tell you what the sun is made of, or one of 
the stars. Of course, you have not a sample of it to 
give him ; how, then, can he possibly find out anything 
about it ? Well, he can tell you something, and this is 
the wonderful discovery that I want to explain to you. 
We now put down the gas, and I kindle a brilliant red 
light. Perhaps some of those whom I see before me 
have occasionally ventured on the somewhat dangerous 
practice of making fireworks. If there is any boy here 
who has ever constructed sky-rockets, and put the little 
balls into the top which are to burn with such vivid 
colors when the explosion takes place, he will know 
that the substance which tinged that red fire must have 
been strontium. He will recognize it by the color ; 
because strontium gives a red light which nothing eke 
will give. Here are some of these lightning papers, as 
they are called ; they are very pretty and very harm- 
less ; and these, too, give brilliant red flashes as I throw 
them. The red tint has, no doubt, been produced by 
strontium also. You see we recognized the substance 
simply by the color of the light it produced when 
burning. 

Perhaps some of you have tried to make a ghost at 
Christmas by dressing up in a sheet, and bearing in 
your hand a ladle blazing with a mixture of common 
salt and spirits of wine, the effect produced being a 
most ghastly one. Some mammas will hardly thank 
me for this suggestion, unless I add that the ghost must 



A STRANGE METAL. 349 

walk about cautiously, for otherwise the blazing spirit 
would be very apt to produce conflagrations of a kind 
more extensive than those intended. However, by the 
kindness of Professor Dewar, I am enabled to show the 
phenomenon on a splendid scale, and also free from all 
danger. I kindle a vivid flame of an intensely yellow 
color, which I think the ladies will unanimously agree 
is not at all becoming to their complexions, while the 
pretty dresses have lost their variety of colors. Here 
is a nice bouquet, and yet you can hardly distinguish 
the green of the leaves from the brilliant colors of the 
flowers, except by trifling differences of shade. Expose 
to this light a number of pieces of variously colored 
ribbon, pink and red and green and blue, and their 
beauty is gone ; and yet we are told that this yellow is 
a perfectly pure color; in fact, the purest color that 
can be produced. I think we have to be thankful that 
the light which our good sun sends us does not possess 
purity of that description. There is one substance 
which will produce that yellow light ; it is a curious 
metal called sodium — a metal so soft that you can cut 
it with a knife, and so light that it will float on water ; 
while, still more strange, it actually takes fire the moment 
it is dropped on the water. It is only in a chemical 
laboratory that you will be likely to meet with the 
actual metallic sodium, yet in other forms the substance 
is one of the most abundant in nature. Indeed, com- 
mon salt is nothing but sodium closely united with a 
most poisonous gas, a few respirations of which would 
kill you. But this strange metal and this noxious gas, 
when united, become simply the salt for our eggs at 



350 STAR-LAND. 

breakfast. This pure yellow light, wherever it is seen, 
either in the flame of spirits of wine mixed with salt or 
in that great blaze at which we have been looking, is 
characteristic of sodium. Wherever you see that par- 
ticular kind of light, you know that sodium must have 
been present in the body from which it came. 

We have accordingly learned to recognize two sub- 
stances, namely, strontium and sodium, by the different 
lights which they give out when burning. To these 
two metals we may add a third. Here is a strip of 
white metallic ribbon. It is called magnesium. It 
seems like a bit of tin at the first glance, but indeed it 
is a very different substance from tin ; for, look, when 
I hold it in the spirit-lamp, the strip of metal immedi- 
ately takes fire, and burns with a white light so dazzling 
that it pales the gas-flames to insignificance. There is 
no other substance which will, when kindled, give that 
particular kind of light which we see from magnesium. 
I can recommend this little experiment as quite suitable 
for trying at home ; you can buy a bit of magnesium 
ribbon for a trifle at the optician's ; it cannot explode 
or do any harm, nor will you get into any trouble with 
the authorities provided you hold it when burning over 
a tray or a newspaper, so as to prevent the white ashes 
from falling on the carpet. 

There are, in nature, a number of simple bodies called 
elements. Every one of these, when ignited under suit- 
able conditions, emits a light which belongs to it alone, 
and by which it can be distinguished from every other 
substance. I do not say that we can try the experiments 
in the simple way I have here indicated. Many of the 



THE USE OE THE PRISM. 351 

materials will yield light which will require to be studied 
by much more elaborate artifices than those which have 
sufficed for us. But you see that the method affords a 
means of finding out the actual substances present in 
the sun or in the stars. There is a practical difficulty 
in the fact that each of the heavenly bodies contains a 
number of different elements; so that in the light it 
sends us the hues arising from distinct substances are 
blended into one beam. The first thing to be done is 
to get some way of splitting up a beam of light, so as 
to discover the components of which it is made. You 
might have a skein of silks of different hues tangled 
together, and this would be like the sunbeam as we 
receive it in its unsorted condition. How shall we 
untangle the light from the sun or a star? I will 
show you by a simple experiment. Here is a beam 
from the electric light; beautifully white and bright, 
is it not? It looks so pure and simple, but yet that 
beam is composed of all sorts of colors mingled together, 
in such proportions as to form white light. I take a 
wedge-shaped piece of glass called a prism, and when I 
introduce it into the course of the beam, you see the 
transformation that has taken place (Fig. 85). Instead 
of the white light you have now all the colors of the 
rainbow — red, orange, yellow, green, blue, indigo, vio- 
let, marked by their initial letters in the figure. These 
colors are very beautiful, but they are transient, for the 
moment we take away the prism they all unite again to 
form white light. You see what the prism has done ; 
it has bent all the light in passing through it ; but it is 
more effective in bending the blue than the red, and 



352 



STAR-LAND. 



consequently the blue is carried away much further 
than the red. Such is the way in which we study the 
composition of a heavenly body. We take a beam of 
its light, we pass it through a prism, and immediately 




Fig. 85. — How to split up a Ray of Light. 



it is separated into its components; then we compare 
what we find with the lights given by the different 
elements, and thus we are enabled to discover the sub- 
stances which exist in the distant object whose light we 
have examined. I do not mean to say that the method 
is a simple one ; all I am endeavoring to show is a 
general outline of the way in which we have discov- 
ered the materials present in the stars. The instrument 
that is employed for this purpose is called the spectro- 



THE NEBULAE. 353 

scope. And perhaps you may remember that name by 
these lines, which I have heard from an astronomical 
friend : — 

" Twinkle, twinkle, little star, 

Now we find ont what yon are, 

When nnto the midnight sky, 

We the spectroscope apply." 

I am sure it will interest everybody to know that 
the elements which the stars contain are not altogether 
different from those of which the earth is made. It is 
true there may be substances in the stars of which we 
know nothing here ; but it is certain that many of the 
most common elements on the earth are present in 
the most distant bodies. I shall only mention one, 
the metal iron. That useful substance has been found 
in some of the stars which lie at almost incalculable 
distances from the earth. 

THE NEBULAE. 

In drawing towards the close of these lectures I must 
say a few words about some dim and mysterious objects 
to which we have not yet alluded. They are what are 
called nebulae, or little clouds ; and in one sense they 
are justly called little, for each of them occupies but 
a very small spot in the sky as compared with that 
which would be filled by an ordinary cloud in our air. 
The nebulae are, however, objects of the most stupen- 
dous proportions. Were our earth and thousands of 
millions of bodies quite as big all put together, they 
would not be nearly so great as one of these nebulae. 



354 STAR-LAND. 

Astronomers reckon up the various nebulae by thou- 
sands, but I must add that most of them are apparently 
faint and uninteresting. A nebula is sometimes liable 
to be mistaken for a comet. The comet is, as I have 
already explained, at once distinguished by the fact 
that it is moving and changing its appearance from 
hour to hour, while scores of years elapse without 
changes in the aspect or position of a nebula. The 




Fig. 86. — The Ring Nebula in Lyra, under Different Telescopic 
Powers. 

most powerful telescopes are employed in observing 
these faint objects. I take this opportunity of showing 
a picture of an instrument suitable for such observa- 
tions. It is the great reflector of the Paris Observa- 
tory (Fig. 87). 

There are such multitudes of nebulae that I can only 
show a few of the more remarkable kinds. In Fig. 86 
will be seen pictures of a curious object in the constel- 
lation of Lyra seen under different telescopic powers. 
This is a gigantic ring of luminous gas. To judge of 
the size of this ring let us suppose that a railway were 
laid across it, and the train you entered at one side was 
not to stop until it reached the other side, how long do 



A GREAT REFLECTING TELESCOPE. 



355 




Fig. 87. — A Great Reflecting Telescope. 



356 STAR-LAND. 

you think this journey would require ? I recollect some 
time ago a picture hi Punch which showed a train about 
to start from London to Brighton, and the guard walk- 
ing up and down announcing to the passengers the 
alarming fact that "this train stops nowhere." An old 
gentleman was seen vainly gesticulating out of the 
window and imploring to be let out ere the frightful 
journey was commenced. In the nebular railway the 
passengers would almost require such a warning. 

Let the train start at a speed of a mile a minute, you 
would think, surely, that it must soon cross the ring. 
But the minutes pass, an hour lias elapsed : so the dis- 
tance must be sixty miles, at all events. The hours 
creep on into days, the days advance into years, and 
still the train goes on. The years would lengthen out 
into centuries, and even when the train had been rush- 
ing on for a thousand years with an unabated speed of 
a mile a minute, the journey would certainly not have 
been completed. Nor do I venture to say what ages 
must elapse ere the terminus at the other side of the 
ring nebula would be reached. 

A cluster of stars viewed in a small telescope will 
often seem like a nebula, for the rays of the stars 
become blended. A powerful telescope will, however, 
dispel the illusion and reveal the separate stars. It 
was, therefore, thought that all the nebulae might be 
merely clusters so exceedingly remote that our mighti- 
est instruments failed to resolve them into stars. But 
this is now known not to be the case. Many of these 
objects are really masses of glowing gas ; such are, for 
instance, the ring nebuke, of which I have just spoken, 



A PRETTY EXPERIMENT. 



357 



and the form of which I can simulate by a pretty 
experiment. 

We take a large box with a round hole cut in one 
face, and a canvas back at the opposite side. I first fill 
this box with smoke, and there are different ways of 
doing so. Burning brown paper does not answer well, 
because the supply of smoke is too irregular and the 
paper itself is apt to blaze. A little bit of phosphorus 
set on fire yields copious smoke, but it would be apt to 




Fig. 88. — How to make the Smoke-rings. 



make people cough, and, besides, phosphorus is a dan- 
gerous thing to handle incautiously, and I do not want 
to suggest anything which might be productive of dis- 
aster if the experiment was repeated at home. A little 
wisp of hay, slightly damped and lighted, will safely 
yield a sufficient supply, and you need not have an 
elaborate box like this ; any kind of old packing-case, 
or even a band-box with a duster stretched across its 
open top and a round hole cut in the bottom, will 
answer capitally. While I have been speaking, my 



358 STAR-LAND. 

assistant has kindly filled this box with smoke, and in 
order to have a sufficient supply, and one which shall 
be as little disagreeable as possible, he has mixed to- 
gether the fumes of hydrochloric acid and ammonia 
from two retorts shown in Fig. 88. A still simpler way 
of doing the same thing is to put a little common salt 
in a saucer and pour over it a little oil of vitriol ; this 
is put into the box, and over the floor of the box com- 
mon smelling-salts is to be scattered. You see there 
are dense volumes of white smoke escaping from every 
corner of the box. I uncover the opening and give a 
push to the canvas, and you see a beautiful ring flying 
across the room ; another ring and another follow. If 
you were near enough to feel the ring, you would expe- 
rience a little puff of wind ; I can show this by blowing 
out a candle which is at the other end of the table. 
These rings are made by the air which goes into a sort 
of eddy as it passes through the hole. All the smoke 
does is to render the air visible. The smoke-ring is 
indeed quite elastic. If we send a second ring hur- 
riedly after the first, Ave can produce a collision, and 
you see each of the two rings remains unbroken, though 
both are quivering from the effects of the blow. They 
are beautifully shown along the beam of the electric 
lamp, or, better still, along a sunbeam. 

We can make many experiments with smoke-rings. 
Here, for instance, I take an empty box, so far as smoke 
is concerned, but air-rings can be driven forth from it, 
though you cannot see them, but you can feel them 
even at the other side of the room, and they will, as 
you see, blow out a candle. I can also shoot invisible 



INVISIBLE RINGS. 359 

air-rings at a column of smoke, and when the missile 
strikes the smoke it produces a little commotion and 
emerges on the other side, carrying with it enough of 
the smoke to render itself visible, while the solid black 
looking ring of air is seen in the interior. Still more 
striking is another way of producing these rings, for I 
charge this box with ammonia, and the rings from it 
you cannot see. There is a column of the vapor of 
hydrochloric acid that also you cannot see ; but when 
the invisible ring enters the invisible column, then a 
sudden union takes place between the vapor of the 
ammonia and the vapor of the hydrochloric acid ; the 
result is a solid white substance in extremely fine dust 
which renders the ring instantly visible. 

WHAT THE NEBULAE ARE MADE OF. 

There is a fundamental difference between the illu- 
mination of these little rings that I have shown you and 
the great rings in the heavens. I had to illuminate our 
smoke with the help of the electric light, for, unless I 
had done so, you would not have been able to see them. 
This white substance formed by the union of ammonia 
and hydrochloric acid has, of course, no more light of 
its own than a piece of chalk ; it requires other light 
falling upon it to make it visible. Were the ring neb- 
ula in Lyra composed of this material, we could not see 
it. The sunlight which illuminates the planets might, 
of course, light up such an object as the ring, if it were 
comparatively near us ; but Lyra is at such a stupen- 
dous distance that any light which the sun could send 



360 STAB-LAND. 

out there would be just as feeble as the light we receive 
from a fixed star. Should we be able to show our smoke- 
rings, for instance, if, instead of having the electric light, 
I merely cut a hole in the ceiling and allowed the feeble 
twinkle of a star in the Great Bear to shine through ? 
In a similar way the sunbeams would be utterly power- 
less to effect any illumination of objects in these stellar 
distances. If the sun were to be extinguished altogether, 
the calamity would no doubt be a very dire one so far 
as we are concerned, but the effect on the other celestial 
bodies (moon and planets excepted) would be of the 
slightest possible description. All the stars of heaven 
would continue to shine as before. Not a point in one 
of the constellations would be altered, not a variation in 
the brightness, not a change in the hue of any star could 
be noticed. The thousands of nebulae and clusters would 
be absolutely unaltered ; in fact, the total extinction of 
the sun would be hardly remarked in the newspapers pub- 
lished in the Pleiades or in Orion. There might possibly 
be a little line somewhere in an odd corner to the effect 
"Mr. So-and-So, our well-known astronomer, has noticed 
that a tiny star, inconspicuous to the eye, and absolutely 
of no importance whatever, has now become invisible." 
If, therefore, it be not the sun which lights up this 
nebula, where else can be the source of its illumination ? 
There can be no other star in the neighborhood adequate 
to the purpose, for, of course, such an object would be 
brilliant to us if it were large enough and bright enough 
to impart sufficient illumination to the nebula. It would 
be absurd to say that you could see a man's face by the 
light of a candle while the candle itself was too faint or 



GEISSLER'S TUBES. 361 

too distant to be visible. The actual facts are, of course, 
the other way ; the candle might be visible, when it was 
impossible to discern the face which it lighted. 

Hence we learn that the ring nebula must shine by 
some light of its own, and now we have to consider 
how it can be possible for such material to be self- 
luminous. The light of a nebula does not seem to be 
like flame; it can, perhaps, be better represented by 
the pretty electrical experiment with Geissler's tubes. 
These are glass vessels of various shapes, and they are 
all very nearly empty, as you will understand when I 
tell you the way in which they have been prepared. A 
little gas was allowed into each tube, and then almost 
all the gas was taken out again, so that only a mere 
trace was left. I pass a current of electricity through 
these tubes, and now you see they are glowing with 
beautiful colors. The different gases give out lights 
of different hues, and the optician has exerted his skill 
so as to make the effect as beautiful as possible. The 
electricity, in passing through these tubes, heats the 
gas which they contain, and makes it glow ; and just 
as this gas can, when heated sufficiently, give out 
light, so does the great nebula, which is a mass of gas 
poised in space, become visible in virtue of the heat 
which it contains. 

We are not left quite in doubt as to the constitution of 
these gaseous nebulae, for we can submit their light to 
the prism in the way I explained when we were speak- 
ing of the stars. Distant though that ring in Lyra may 
be, it is interesting to learn that the ingredients from 
which it is made are not entirely different from sub- 



362 STAR-LAND. 

stances we know on our earth. The w r ater in this glass, 
and every drop of water, is formed by the union of two 
gases, of which one is hydrogen. This is an extremely 
light material, as you see by a little balloon which 
ascends so prettily when filled with it. Hydrogen also 




Fig. 89. — The Pleiades. 

burns very readily, though the flame is almost invisible. 
When I blow a jet of oxygen through the hydrogen, I 
produce a little flame with a very intense heat. For 
instance, I hold a steel pen in the flame, and it glows 
and sputters, and falls down in white-hot drops. It is 
needless to say that, as a constituent of water, hydrogen 
is one of the most important elements on this earth. It 
is, therefore, of interest to learn that hydrogen in some 
form or other is a constituent of the most distant objects 
in space that the telescope has revealed. 

PHOTOGRAPHING THE NEBULiE. 

Of late years we have learned a great deal about 
nebulae, by the help which photography has given to 



PHOTOGRAPHING THE NEBULAE. 363 

us. Look at this group of stars which constitutes that 
beautiful little configuration known as the Pleiades 
(Fig. 89). It looks like a miniature representation of 
the Great Bear ; in fact, it would be far more appropri- 
ate to call the Pleiades the Little Bear than to apply 
that title to another quite different constellation, as has 
unfortunately been done. The Pleiades form a group 
containing six or seven stars visible to the ordinary eye, 
though persons endowed with exceptionally good vision 
can usually see a few more. In an opera-glass the 
Pleiades becomes a beautiful spectacle, though in a large 
telescope the stars appear too far apart to make a really 
effective cluster. When Mr. Roberts took a photograph 
of the Pleiades he placed a highly sensitive plate in his 
telescope, and on that plate the Pleiades engraved their 
picture with their own light. He left the plate exposed 
for hours, and on developing it not only were the stars 
seen, but there were also patches of faint light due to the 
presence of nebula. It could not be said that the objects 
on the plate were fallacious, for another photograph was 
taken, when the same appearances were reproduced. 

When we look at that pretty group of stars which 
has attracted admiration during all time, we are to 
think that some of those stars are merely the bright 
points in a vast nebula, invisible to our unaided eyes 
or even to our mighty telescopes, though capable of 
recording its trace on the photographic plate. Does not 
this give us a greatly increased notion of the extent of 
the universe, when we reflect that by photography we 
are enabled to see much which the mightiest of tele- 
scopes had previously failed to disclose ? 



364 STAR-LAND. 

Of all the nebulae, now numbering some thousands, 
there is but a single one which can be seen without a 
telescope. It is in the constellation of Andromeda, and 
on a clear dark night can just be seen with the unaided 
eye as a faint stain of light on the sky. It has hap- 
pened before now that persons noticing this nebula for 
the first time have thought they had discovered a comet. 
I would like you to try and find out this object for 
yourselves. 

If you look at it with an opera-glass it appears to be 
distinctly elongated. You can see more of its structure 
when you view it in larger instruments, but its nature 
was never made clear until some beautiful photographs 
were taken by Mr. Roberts (Fig. 90). Unfortunately, 
the nebula in Andromeda has not been placed in the 
best position for its portrait from our point of view. It 
seems as if it were a rather flat-shaped object, turned 
nearly edgewise towards us. To look at the pattern on 
a plate, you would naturally hold the plate so as to be 
able to look at it squarely. The pattern would not be 
seen well if the plate were so tilted that its edge was 
turned towards you. That seems to be nearly the way 
in which, we are forced to view the nebula in Androm- 
eda. We can trace in the photograph some divisions 
extending entirely round the nebula, showing that it 
seems to be formed of a series of rings ; and there are 
some outlying portions which form part of the same 
system. Truly this is a marvellous object. It is 
impossible for us to form any conception of the true 
dimensions of this gigantic nebula ; it is so far off that 
we have never yet been able to determine its distance. 



THE NEBULA IN ANDROMEDA. 365 

Indeed, I may take this opportunity of remarking that 
no astronomer has yet succeeded in ascertaining the 




Fig. 90. — The Great Nebula in Andromeda. 

(From Mr. Robert*' Photograph.) 

distance of any nebula. Everything, however, points 
to the conclusion that they are at least as far as the 
stars. 

It is almost impossible to apply the methods which 
we use in finding the distance of a star to the discovery 



366 STAR-LAND. 

of the distance of the nebulce. These flimsy bodies are 
usually too ill-defined to admit of being measured with 
the precision and the delicacy required for the deter- 
mination of distance. The measurements necessary for 
this purpose can only be made from one star-like point 
to another similar point. If we could choose a star in 
the nebula and determine its distance, then, of course, 
we should have the distance of the nebula itself; but 
the difficulty is that we have, in general, no means of 
knowing whether the star does actually lie in the object. 
It may, for anything we can tell, lie billions of miles 
nearer to us, or billions of miles further off, and, by 
merely happening to lie in the line of sight, appear to 
glimmer in the nebula itself. 

If we have any assurance that the star is surrounded 
by a mass of this glowing vapor, then it may be possible 
to measure that nebula's distance. It will occasionally 
happen that grounds can be found for believing that a 
star which appears to be in the glowing gas does veri- 
tably lie therein, and is not merely seen in the same 
direction. There are hundreds of stars visible on a 
good drawing or a good photograph of the famous 
object in Andromeda, and doubtless large numbers of 
these are merely stars which happen to lie in the same 
line of sight. The peculiar circumstances attending 
the history of one star seem, however, to warrant us 
in making the assumption that it was certainly in the 
nebula. The history of this star is a remarkable one. 
It suddenly kindled from invisibility into brilliancy. 
How is a change so rapid in the lustre of a star to be 
accounted for ? In a few days its brightness had under- 



THE DISTANCE OF A NEBULA. 367 

gone an extraordinary increase. Of course, this does 
not tell us for certain that the star lay in the glowing 
gas ; but the most rational explanation that I have 
heard offered of this occurrence is that due, I believe, 
to my friend Mr. Monck. He has suggested that the 
sudden outbreak in brilliancy might be accounted for 




Fig. 91. — To show how Small the Solar System is compared with 
a Great Nebula. 

on the same principles as those by which we explain the 
ignition of meteors in our atmosphere. If a dark star, 
moving along with terrific speed through space, were 
suddenly to plunge into a dense region of the nebula, 
heat and light must be evolved in sufficient abundance 
to transform the star into a brilliant object. If, there- 
fore, we knew the distance of this star at the time it 
was in Andromeda, we should, of course, learn the 
distance of that interesting object. This has been 
attempted, and it has thus been proved that the Great 
Nebula must be very much further from us than is that 



368 STAR-LAND. 

star of whose distance I attempted some time ago to 
give you a notion. 

We thus realize the enormous size of the Great 
Nebula. It appears that if, on a map of this object, we 
were to lay down, accurately to scale, a map of the solar 
system, putting the sun in the centre and all the planets 
around in their true proportions out to the boundary 
traced by Neptune, this area, vast though it is, would 
be a mere speck on the drawing of the object. Our 
system would have to be enormously bigger before it 
sufficed to cover anything like the area of the sky 
included in one of these great objects. Here is a sketch 
of a nebula (Fig. 91), and near it I have marked a dot 
which is to indicate our solar system. We may feel 
confident that the Great Nebula is at the very least as 
mighty as this proportion would indicate. 

CONCLUSION. 

And now, my young friends, I am drawing near the 
close of that course of lectures which has occupied us, 
I hope you will think not unprofitably, for a portion of 
our Christmas holidays. We have spoken of the sun 
and of the moon, of comets and of stars, and I have 
frequently had occasion to allude to the relative position 
of our earth in the universe. No doubt it is a noble 
globe which we inhabit, but I have failed in my purpose 
if I have not shown you how insignificant is this earth 
when compared with the vast extent of some of the 
other bodies that abound in space. We have, however, 
been endowed with a feeling of curiosity which makes 



HOW LITTLE AVE ARE. 369 

us long to know of things beyond the confines of our 
own earth. Astronomers can tell us a little, but too 
often only a little. They will say — That is a star, and 
That is a planet, and That is so big, and That so far ; 
such is the meagre style of information with which we 
often have to be content. The astronomers who live on 
other worlds, if their faculties be in any degree com- 
parable with ours, must be similarly ignorant with 
regard to this earth. Inhabitants of our fellow-planets 
can know hardly anything more than that the earth on 
which we dwell is a globe 8000 miles across, with 
many clouds around us. Some of the planets would 
not even pay us the compliment of recognizing our 
existence ; while from the other systems — the countless 
other systems — of space we are absolutely impercep- 
tible and unknown. 

Out of all the millions of bodies which we can see, 
you could very nearly count on your fingers those from 
which our earth would be visible. This reflection is 
calculated to show us how^ vast must be the real extent 
of that universe around us. Here is our globe, with its 
inhabitants, with its great continents, with its oceans, 
with its empires, its kingdoms, with its arts, its com- 
merce, its literature, its sciences, and yet it w r ould seem 
that all these things are absolutely unknown to any 
inhabitants that may exist elsewhere. I do not think 
that any reasonable person will doubt that there must 
be inhabitants elsewhere. There are millions of globes, 
many of them more splendid than ours. Surely it 
would be presumptuous to say that this is the only 
one of all the bodies in the universe on the surface of 



370 STAR-LAND. 

which life, with all that life involves, is manifested. 
You will rather think that our globe is but one in the 
mighty fabric, and that other globes may teem with 
interest just as ours does. We can, of course, make 
no conjecture as to what the nature of the life may be 
elsewhere. Could a traveller visit some other globes 
and bring back specimens of the natural objects that he 
found there, no collections that the world has ever seen 
could rival them in interest. When I go into the Brit- 
ish Natural History Museum and look around that 
marvellous collection, it awakens in me a feeling of 
solemnity. I see there the remains of mighty extinct 
animals which once roamed over this earth ; also objects 
which have been dredged from the bottom of the sea at 
a depth of some miles ; there I can examine crystals 
which have required incalculable ages for their forma- 
tion ; and there I look at meteorites which have travelled 
from the heavens above down on to the earth beneath. 
Such sights, and the reflections they awaken, bring 
before us in an imposing manner the phenomena of our 
earth, and the extent and interest of its past history. 
Oliver Wendell Holmes said that the only way to see 
the British Museum was to take lodgings close by when 
you were a boy, and to stay in the Museum from nine 
to five every day until you were an old man ; then you 
would begin to have some notion of what this Institu- 
tion contains. Think what millions of British Museums 
would be required were the universe to be adequately 
illustrated : one museum for the earth, another for 
Mars, another for Venus — but it would be useless 
attempting to enumerate them! 



GEOGRAPHY AND HISTORY. 371 

Most of us must be content with acquiring the 
merest shred of information with regard even to our 
own earth. Perhaps a schoolboy will think it fortunate 
that we are so ignorant with respect to the celestial 
bodies. What an awful vista of lessons to be learned 
would open before his view, if only we had a competent 
knowledge of the other globes which surround us in 
space ! I should like to illustrate the extent of the 
universe by following this reflection a little further. 
I shall just ask you to join with me in making a little 
calculation as to the extent of the lessons you would 
have to learn if astronomers should succeed in discov- 
ering some of the things they want to know. 

Of course, all of us learn geography and history. 
We must know the geography of the leading coun- 
tries of the globe, and we must have some knowledge 
of their inhabitants and of their government, their 
resources and their civilization. It would seem shock- 
ingly ignorant not to know something about China, or 
not to have some ideas on the subject of India or Egypt. 
The discovery of the New World also involves matters 
on which every boy and girl has to be instructed. Sup- 
posing we were so far acquainted with the other globes 
scattered through space that we were able to gain some 
adequate knowledge of their geography and natural his- 
tory, of the creatures that inhabit them, of their differ- 
ent products and climates, then everybody would be 
anxious to learn those particulars ; and even when the 
novelty had worn off, it would still be right for us to 
know something about countries perhaps more populous 
than China, about nations more opulent than our own, 



372 STAR-LAND. 

about battles mightier than Waterloo, about animals 
and plants far stranger than any we have ever dreamt 
of. An outline of all such matters should, of course, 
be learned, and as the amount of information would be 
rather extensive, we will try to condense it as much as 
possible. 

To aid us in realizing the full magnificence of that 
scheme in the heavens of which Ave form a part, I shall 
venture to give an illustration. Let us attempt to form 
some slight conception of the number and of the bulk 
of the books which would be necessary for conveying 
an adequate description of that marvellous universe of 
stars which surround us. These stars being suns, and 
many of them being brighter and larger than our own 
sun, it is but reasonable to presume that they may be 
attended by planetary systems. I do not say that we 
have any right to infer that such systems are like ours. 
It is not improbable that many of the suns around us 
have a much poorer retinue than that which dignifies 
our sun. On the other hand, it is just as likely that 
many of these other suns may be the centres of systems 
far more brilliant and interesting, with far greater diver- 
sity of structure, with far more intensity and variety 
of life and intelligence than are found in the system of 
which we form a part. It is only reasonable for us to 
suppose that, as our earth is an average planet, so our 
sun is an average star both in size and in the impor- 
tance of its attendants. We may take the number of 
stars in the sky at about one hundred millions ; and 
thus we see that the books which are to contain a 
description of the entire universe — or rather, I should 



A UNIVERSAL LIBRARY. 373 

say, of the entire universe that we see — must describe 
100,000,000 times as much as is contained in our single 
system. Of course, we know next to nothing of what 
the books should contain ; but we can form some con- 
jecture of the number of those books, and this is the 
notion to which I now ask your attention. 

So vast is the field of knowledge that has to be trav- 
ersed, that we should be obliged to compress our de- 
scriptions into the narrowest compass. We begin with 
a description of our earth, for nearly all the books in 
the libraries that exist at this moment are devoted to 
subjects connected with this earth. They include vari- 
ous branches of history, innumerable languages and liter- 
atures and religions, everything relating to life on this 
globe, to its history in past geological times, to its geog- 
raphy, to its politics, to every variety of manufacture 
and agriculture, and all the innumerable matters which 
concern our earth's inhabitants, past and present. But 
this tremendous body of knowledge must be much con- 
densed before it would be small enough to retire to its 
just position in the great celestial library. I can only 
allow to the earth one volume of about 500 pages. 
Everything that has to be said about our earth must be 
packed within this compass. AH terrestrial languages, 
histories, and sciences that cannot be included between 
its covers can find no other place on our shelves. I can- 
not spare any more room. Our celestial library will be 
big enough, as you shall presently see. I am claiming 
a good deal for our earth when I regard it as one of the 
most important bodies in the solar system. Of course 
it is not the biggest — very far from it ; but it seems as 



374 STAR-LAND. 

if the big planets and the sun were not likely to be 
inhabited, so that if we allow one other volume to the 
rest of the solar system, it will perhaps be sufficient, 
though it must be admitted that Venus, of which we 
know next to nothing, except that it is as large as the 
earth, may also be quite as full of life and interest. 
Mars and Mercury are also among the planets with 
possible inhabitants. We are, therefore, restricting the 
importance of the solar system as much as possible, per- 
haps even too much, by allowing it two. Within those 
two volumes every conceivable thing about the entire 
solar system — sun, planets (great and small), moons, 
comets, and meteors — must be included, or else it 
would not be represented at all in the great celestial 
library. 

We shall deal on similar principles with the other 
systems through space. Each of the 100,000,000 stars 
will have two volumes allotted to it. Within the two 
volumes devoted to each star we must compress our 
description of the body itself and of the system which 
surrounds it; the planets, their inhabitants, histories, 
arts, sciences, and all other information. I am not, 
remember, discussing the contents, but only the number 
of books we should have to read ere we could obtain 
even the merest outline of the true magnificence of the 
heavens. Let us try to form some estimate as to the 
kind of library that would be required to accommodate 
200,000,000 volumes. I suppose a long straight hall, 
so lofty that there could be fifty shelves of books on each 
side. As you enter you look on the right hand and on 
the left, and you see it packed from floor to ceiling with 



A LIBRARY FIFTY MILES LONG. 375 

volumes. We have arranged them according to the 
constellations. All the shelves in one part contain 
the volumes relating to the worlds in the Great 
Bear, while upon the other side may repose ranks 
upon ranks of volumes relating to the constellation of 
Orion. 

I shall suppose that the volumes are each about an 
inch and a half thick, and as there are fifty shelves on 
each side, you will easily see that for each foot of its 
length the hall will accommodate 800 books. We can 
make a little calculation as to the length of this library, 
which, as we walk down through it, stretches out before 
us in a majestic corridor, with books, books everywhere. 
Let us continue our stroll, and as we pass by we find 
the shelves on both sides packed with their thousands 
of volumes ; and we walk on and on, and still see no 
end to the vista that ever opens before us. In fact, no 
building that was ever yet constructed would hold this 
stupendous library. Let the hall begin on the furthest 
outskirts of the west of London, carry it through the 
heart of the city, and away to the utmost limits of the 
east — not a half of the entire books could be accom- 
modated. The mighty corridor would have to be fifty 
miles long, and to be packed from floor to ceiling with 
fifty shelves of books on each side, if it is to contain 
even this very inadequate description of the contents 
of the visible universe. Imagine the solemn feelings 
with which we should enter such a library, could it 
be created by some miracle ! As we took down one of 
the volumes, with what mysterious awe should we open 
it, and read therein of some vast world which eye had 



376 STAR-LAND. 

never seen ! There we might learn strange problems 
in philosophy, astonishing developments in natural his- 
tory ; with what breathless interest w r e should read of 
inhabitants of an organization utterly unknown to our 
merely terrestrial experience ! Notwithstanding the 
vast size of the library, the description of each globe 
would have to be very scanty. Thus, for instance, in 
the single book which referred to the earth I suppose a 
little chapter might be spared to an island called Eng- 
land, and possibly a page or so to its capital, London. 
Similarly meagre would have to be the accounts of the 
other bodies in the universe ; and yet, for this most 
inadequate of abstracts, a library fifty miles long, and 
lined closely with fifty shelves of books on each side, 
would be required ! 

Methuselah lived, we are told, nine hundred and 
sixty-nine years ; but even if he had attained his 
thousandth birthday he would have had to read about 
300 of these books through every day of his life before 
he accomplished the task of learning even the merest 
outline about the contents of space. 

If, indeed, we were to have a competent knowledge 
of all these other globes, of all their countries, their 
geographies, their nations, their climates, their plants, 
their animals, their sciences, languages, arts and litera- 
tures, it is not a volume, or a score of volumes, that 
would be required, but thousands of books would have 
to be devoted to the description of each world alone, 
just as thousands of volumes have been devoted to the 
affairs of this earth without exhausting the subjects of 
interest it presents. Hundreds of thousands of libra- 



THE UNKNOWN OUTSIDE. 377 

ries, each as large as the British Museum, would not 
contain all that should be written, were we to have 
anything like a detailed description of the universe 
which we see, I specially emphasize the words just 
written, and I do so because the grandest thought of 
all, and that thought with which I conclude, brings 
before us the overwhelming extent of the unseen uni- 
verse. Our telescopes can, no doubt, carry our vision 
to an immeasurable distance into the depths of space. 
But there are, doubtless, stars beyond the reach of our 
mightiest telescopes. There are stars so remote that 
they cannot record themselves on the most sensitive 
of photographic plates. 

On the blackboard I draw a little circle with a piece 
of chalk. I think of our earth as the centre, and this 
circle will mark for us the limit to which our greatest 
telescopes can sound. Every star which we see, or 
which the photographic plate sees, lies within this 
circle ; but, are there no stars outside ? It is true 
that we can never see them, but it is impossible to 
believe that space is utterly void and empty where it 
lies beyond the view of our telescopes. Are we to 
say that inside this circle stars, worlds, nebulae, and 
clusters are crowded, and that outside there is nothing ? 
Everything teaches us that this is not so. We 
occasionally gain accession to our power by adding 
perhaps an inch to the diameter of our object-glass, or 
by erecting a telescope in an improved situation on 
a lofty mountain peak, or by procuring a photo- 
graphic plate of increased sensibility. It thus happens 
that we are enabled to extend our vision a little 



378 STAE-LAND. 

further and to make this circle a little larger, and 
thus to add a little more to the known inside which 
has been won from the unknown outside. Whenever 
this is done we invariably find that the new region 
thus conquered is also densely filled with stars, with 
clusters, and with nebulae ; it is thus unreasonable to 
doubt that the rest of space also contains untold 
myriads of objects, even though they may never, by 
any conceivable improvement in our instruments, be 
brought within the range of our observation. Reflect 
that this circle is comparatively small with respect to 
the space outside. It occupied but a small spot on this 
blackboard, the blackboard itself occupies only a small 
part of the end of the theatre, while the end of the 
theatre is an area very small compared with that of 
London, of England, of the world, of the solar system, 
of the actual distance of the stars. In a similar way 
the region of space which is open to our inspection is 
an inconceivably small portion of the entire extent of 
space. The unknown outside is so much larger than 
the known inside, it is impossible to express the pro- 
portion. I write down unity in this corner and a 
cipher after it to make ten, and six ciphers again to 
make ten millions, and again, six ciphers more to make 
ten billions ; but I might write six more, ay, I might 
cover the whole of this blackboard with ciphers, and 
even then I should not have got a number big enough 
to express how greatly the extent of the space we can- 
not see exceeds that of the space we can see. If, there- 
fore, we admit the fact, which no reasonable person can 
doubt, that this outside, this unknown, this unreachable 



THE MAJESTY OF THE UNIVERSE. 379 

and, to us, invisible space does really contain worlds 
and systems as does this small portion of space in 
which we happen to be placed — then, indeed, we 
shall begin truly to comprehend the majesty of the 
universe. What figures are to express the myriads 
of stars that should form a suitable population for a 
space inconceivably greater than that which contains 
100,000,000 stars? But our imagination will extend 
still further. It brings before us these myriads of 
unseen stars with their associated worlds, it leads us 
to think that these worlds may be full to the brim 
with interests as great as those which exist on our 
world. When we remember that, for an adequate 
description of the worlds which we can see, one hun- 
dred thousand libraries, each greater than any library 
on earth, would be utterly insufficient, what conception 
are we to form when we now learn that even this would 
only amount to a description of an inconceivably small 
fragment of the entire universe ? 

Let us conceive that omniscience granted to us an 
adequate revelation of the ample glories of the heavens, 
both in that universe which we do see and in that infi- 
nitely greater universe which we do not see. Let a full 
inventory be made of all those innumerable worlds, with 
descriptions of their features and accounts of their inhab- 
itants and their civilizations, their geology and their 
natural history, and all the boundless points of interest 
of every kind which a world in the sense in which 
we understand it does most naturally possess. Let 
those things be written every one, then may we say 
that were this whole earth of ours covered with vast 



380 STAR-LAND. 

buildings, lined from floor to ceiling with book-shelves 
— were every one of these shelves stored full with 
volumes, yet, even then this library would be inade- 
quate to receive the books that would be necessary 
to contain a description of the glories of the sidereal 
heavens. 



CONCLUDING CHAPTER. 

HOW TO NAME THE STARS. 

Every one who wishes to learn something about 
astronomy should make a determined effort to become 
acquainted with the principal constellations, and to 
find out the names of the brighter and more interest- 
ing stars. I have therefore added to Star-land this 
little chapter, in which I have tried to make the study 
of the stars so simple that, by taking advantage of a 
few clear nights, there ought to be no difficulty in 
obtaining a knowledge of a few constellations. 

The first step is to become familiar with the Great 
Bear, or Ursa Major, as astronomers more generally 
call the group. We begin with this, because after it 
has been once recognized, then you will find it quite 
easy to make out the other constellations and stars. 
It may save you some trouble if you can get some one 
to point out to you the Great Bear ; but even without 
such aid, I think you will be able to make out the 
seven bright stars which form this remarkable group, 
from the figure here given (Fig. 92). Of course, the 
position of this constellation, as of every other in the 
heavens, changes with the hour of the night, and 
changes with the seasons of the year. About April the 
constellation at 11 o'clock at night is high over your 
head. In September at the same hour, the Great Bear 
is low down in the north. It is to be seen in the west 

381 



382 



STAR-LAND. 



in July, and at Christmas it lies in the east at conven- 
ient hours in the evening for observation. One of the 
advantages of using the Great Bear as the foundation 




Fig. 92. — The Great Bear and the Pole Star. 



of our study of the stars arises from the fact that to an 
observer in the British Islands or in similar latitudes 
this group never sets. Whenever the sky is clear after 
nightfall, the Great Bear is to be seen somewhere, 
while the brightness of its component stars makes it a 
conspicuous object. Indeed, there is only one constel- 



THE POLE STAR. 383 

lation in the sky, namely, that of Orion, which is a 
more brilliant group than the Great Bear. We shall 
tell you about Orion presently, but it does not suit to 
begin with, because it can only be seen in winter, and 
is then placed very low down in the heavens. 

Your next lesson will be to utilize the Great Bear 
for the purpose of pointing out the Pole Star. Look 
at the two stars marked a and /3. They are called the 
" Pointers," because if you follow the direction they 
indicate along the dotted line in the figure, they will 
conduct your glance to the Pole. This is the most 
important star in the heavens to astronomers, because 
it happens to mark very nearly the position of the Pole 
on the sky. You will easily note the peculiarity of 
the Pole Star if you will look at it two or three times 
in the course of the night. It will appear to remain in 
the same place in the sky, while the other stars change 
their places from hour to hour. It is very fortunate 
that we have a star like this in the northern heavens ; 
the astronomers in Australia or New Zealand can see 
no bright star lying near the Southern Pole which will 
answer the purposes that the Pole Star does so conven- 
iently for us in the north. 

The Pole Star belongs to a constellation which we 
call the Little Bear ; two other conspicuous members 
of this group are the two " Guards" ; you will see how 
they are situated from Fig. 82, p. 322. They lie 
nearly midway between the Pole Star and the last of 
the three stars which form the Great Bear's Tail. The 
same figure will also introduce us to another beautiful 
constellation, namely, Cassiopeia. You will never find 



384 STAR-LAND. 

any difficulty in identifying the figure that marks this 
group if you will notice that the Pole lies midway 
between it and the Great Bear. 

Cassiopeia is also one of the constellations that never 
set to British observers ; but now we have to speak of 



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Fig. 93. — The Great Square of Pegasus. 

groups which do set, and which, therefore, can only be 
observed when the proper season comes round. The 
first of these is " the Great Square of Pegasus " ; you 
cannot see this group conveniently in the spring or 
summer, but during the autumn and winter it is well 
placed after nightfall. There are four conspicuous stars 
forming the corners of the square, and then three others 
marked a, 7, and ft (Fig. 93), which form a sort of handle 
to the square. In fact, if you once recognize this group, 
you will perhaps see in it a resemblance to a great 
saucepan with a somewhat bent handle, and then you 



THE GREAT SQUARE OF PEGASUS. 385 

will be acquainted with a large tract of Star-land near 
the Square of Pegasus. From the figure you will see 
that a line imagined to be drawn from the Pole Star 
over the end of Cassiopeia, and then produced as far 
again, will just lead to the Great Square. I have also 
marked on this figure two objects that are of great tele- 
scopic interest ; one of them is the Nebula in Andromeda, 
of which we had an account in the last lecture. You 
see it lies halfway between the corner a of the square 
and the group of Cassiopeia. Another interesting object 
is the star marked 7 Andromedse. The telescope shows 
it to consist of a pair of stars, the colors of which are 
beautifully contrasted. 

At the end of this handle to the Great Square of 
Pegasus is the star a, in the constellation of Perseus. 
It lies between two other stars 7 and 8. We refer to 
Fig. 84, in which these stars are shown. We there 
employed the figure to indicate the position of Algol, 
the remarkable variable star. Your map will also 
point out some other important stellar features. If 
we curve round the three marked 7, a, and S of 
Perseus, the eye is conducted to Capella, a gem of the 
first magnitude in the constellation of Auriga. Close 
to Capella is a long triangle, the corners of which are 
the " Hoedi," the three kids — which Capella is supposed 
to nurture. 

If we carry a curve through 7, a, S, of Perseus, and 
now bend it in the opposite way, the eye is led through 
€ and £ in the same constellation, and then on to the 
Pleiades, of which we have already spoken. 

Perseus lies in one of the richest parts of the heavens. 



386 



STAR-LAND. 





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/ 1 -** 




/ I 




/ 




/ 




The Belt of ,• ; / 
/ (prion >#' € J 


/ 


» b ,-&The Gfeat / 
/ Nebuja / 
/ in Orion/ 
1 ' / 


/ 


/ 


# 


ZZZZr.-z- # Rigel 


Sirius 
1st. Ma^ 


P 1st. Mag 



Fig. 94. — Orion and Sirius. 



OBSERVING THE PLEIADES. 387 

The Milky Way stretches across the group, and the sky 
is strewn with stars beyond number. Even an opera- 
glass directed to this teeming constellation cannot fail 
to afford the observer a delightful glimpse of celestial 
scenery. 

We may, however, specially remind the beginner that 
the objects on this map are not always to be seen, and 
as an illustration of the way in which the situation and 
the visibility of the constellations are affected by the 
time of year, I shall take the case of the Pleiades and 
follow them through a season. Let us suppose that we 
make a search for this group at 11 p.m. every night. 
On the 1st of January, the Pleiades will be found high 
up in the sky in the southwest. On the 1st of March, 
they will be setting in the west at the same hour. On 
the 1st of May, the Pleiades are not visible, neither 
are they on the 1st of July. On the 1st of September, 
they will be seen low down in the east. On the 1st 
of November, they will be high in the heavens in the 
southeast. On the ensuing 1st of January, the Pleiades 
will be found back in the same place which they occu- 
pied on the same date in the preceding year, and so 
on throughout the cycle. Of course, you will not sup- 
pose that their changes are due to actual motions 
in the group of stars themselves. They are merely 
apparent, and are to be explained by the motion of 
the earth round its axis, and the revolution around 
the sun. 

Next we are to become acquainted with the glory 
of our winter skies, the constellation of Orion, Fig. 94. 
I dare say many of my readers are already familiar with 



388 STAR-LAND. 

the well-known twin stars which form the belt of Orion, 
but if not, they will be able to recognize it by the help 
of the groups already learned. Imagine a line drawn 
from the Pole Star through Capella, and then produced 
as much further again, and we shall be conducted into 
the precincts of Orion. This group lies on the equa- 
tor, and, consequently, it is equally familiar to southern 
astronomers and to those of the north. It can be best 
seen by those who observe it from or near the equator. 

The brightest star in Orion is known either as a 
Orionis or as Betelgeuze, by which name it is repre- 
sented in the figure. This star is of the first magni- 
tude, and so is Rigel on the opposite side of the belt. 
The three stars of the belt and the two others, 7 and 
/c, at which they point above and below, are of second 
magnitude. 

The owner of a telescope finds especial attractions in 
this constellation. Notably among the subjects which 
will interest him is the Great Nebula, the position of 
which is indicated in our figure. Under the middle 
of the belt are a few stars, around which is a hazy 
light that is perceptible with the smallest telescopic 
aid. Viewed by instruments of adequate proportions, 
these have developed into a marvellous nebula of glow- 
ing gas, attaining to dimensions so vast that no one has 
yet ever attempted to estimate them. 

The vicinity of Orion is also enriched with some of 
the most interesting stellar objects. Follow the line of 
the belt upwards to the right, and your eye is conducted 
to a ruddy first magnitude star named Aldebaran, in 
the constellation of the Bull. This is a pleasing object, 



MAKE YOUE OWN MAPS. 389 

which the beginner will sometimes be apt to confuse 
with the planet Mars, to which, under certain circum- 
stances, it certainly bears a resemblance. Another' very 
pleasing little group, known as the Hyades, will be found 
near Aldebaran. If the line of the belt of Orion be car- 
ried down to the left, it will be found to point to Sirius, 
or the Dog Star. 

You will find it an interesting occupation to make 
for yourself maps of small parts of the heavens. First 
copy out the chief stars in their proper places from the 
star atlas, and then fill in the smaller stars with your 
own observations. Try first on some limited region of 
the heavens ; take the figure of Cassiopeia, for instance, 
or the Square of Pegasus, and see if you can produce a 
fair representation of those groups by marking in the 
stars that your instrument will show you ; or take the 
Pleiades and make a tracing of the principal stars of 
the group from the sketch that we have given (Fig. 89), 
then take an opera-glass and fill in as carefully as you 
can all that it will show. I can assure you that you 
will find a little definite work of this kind full of 
interest and instruction. 

But I hope you will desire to advance further in the 
study of the heavens. It is to be remembered that with 
even the most moderate instruments there is much to 
be done. Many comets have been detected, and many 
planets have been discovered, by the use of telescopes 
so small that they could be easily carried out from the 
house for the evening's work and brought back again 
after the observations were over. 

It remains for me to add a few words which will help 



390 STAR-LAND. 

you in finding the planets. It is, of course, impossible 
to represent such objects as Jupiter, Saturn, Venus, 
Mars, and Mercury on maps of the heavens, because 
these bodies are constantly moving about, and if their 
places were right to-day they would be wrong to-mor- 
row. The almanac will be necessary for you here. You 
must find out by its help what planets are visible and 
in what part of the sky they are placed. Then you will 
have to compare your maps with the heavens, and when 
you find a bright star-like body that is not shown on 
your maps you may conclude at once that it is the 
planet. Although these objects are so star-like to the 
unaided eye, yet the resemblance is at once dispelled 
when we use a telescope. The star is only a bright 
point of light and white, the planet shows a visible 
shape. This is, at least, the case with the five planets 
I have named ; for there are others, such as Uranus and 
Neptune, which are too far to be much more than star- 
like points in ordinary telescopes. The minor planets 
would not interest you. 

I hope that the reading of Star-land will, at all 
events, induce you to make a beginning of the study 
of the heavens, if you have not already done so. If 
you have the advantage of a telescope, so much the 
better ; but, if this is impossible, make the best use of 
your own eyes. Do not put it off or wait till you get 
some one to teach you. If it be clear this very night, 
go out and find the Great Bear and the Pole Star, and 
as many of the other constellations as you can, and at 
once commence your career as an astronomer. 



USEFUL ASTRONOMICAL FACTS. 



391 



TABLE OF USEFUL ASTRONOMICAL FACTS. 

The sun's mean distance from the earth is 92,700,000 
miles ; his diameter is 865,000 miles, and he rotates in 
a period between 25 and 26 days. 

The moon's mean distance from the earth is 238,000 
miles; the diameter of the moon is 2160 miles, and the 
time of revolution round the earth is 27.322 days. 

THE PLANETS. 





Mean Dis- 










tance from 


Periodic Time 


Diameter 






the Sun in 


of Revolution 


of Planet 


Axial Rotation. 




Millions of 


in Days. 


in Miles. 






Miles. 
















Hrs. Mins. Sees. 


Mercury . . 


35.9 


87.969 


2,992 


Uncertain. 


Venus . 






67.0 


224.70 


7,660 


Uncertain. 


Earth . 






92.7 


365.26 


7,918 


23 56 4.09 


Mars . 






141 


686.98 


4,200 


24 37 22.7 


Jupiter 






482 


4,332.6 


85,000 


9 55 - 


Saturn 




884 


10,759 


71,000 


10 14 23.8 


Uranus 




1,780 


30,687 


31,700 


Unknown. 


Neptune 




2,780 


60,127 


34,500 


Unknown. 



THE SATELLITES OF MARS. 



Name. 


Mean Distance from 
Centre of Mars. 


Periodic Time. 


Phobos 

Deimos 


5,800 miles. 
14,500 " 


Hrs. Mins. Sees. 

7 39 14 
30 17 54 



392 



STAR-LAND. 



THE SATELLITES OF JUPITER, 



Name. 


Mean Distance from 
Centre of Jupiter. 


Periodic Time. 


I . 


262,000 miles. 
417,000 " 
664,000 " 
1,170,000 " 
112,400 " 


Days Hrs. Mins. Sees. 
1 18 27 34 


II 

Ill 

IV 

V 


3 13 13 42 

7 3 42 33 
16 16 32 11 
— 11 57 (?) 



THE SATELLITES OF SATURN. 



Name. 



Mimas . 
Enceladus 
Tethys . 
Dione 
Rhea . . 
Titan . . 
Hyperion 
Iapetus . 



Mean Distance from 
Centre of Saturn. 



118,000 miles. 
152,000 
188,000 
241,000 
337,000 
781,000 
946,000 
2,280,000 



Periodic Time. 



Days 

1 
1 

2 

4 

15 

21 

79 



21 

17 
12 

22 
7 
7 



Mins. 

37 
53 
18 
41 
25 
41 
7 
54 



Sees. 

27.9 
6.7 
25.7 
8.9 
10.8 
25.2 
40.8 
40.4 



A ninth satellite was discovered in August, 1898, by Prof. W. 
H. Pickering, but its mean distance and periodic time have not 
yet been determined with precision. 



THE SATELLITES OF URANUS. 



Name. 


Mean Distance from 
Centre of Uranus. 


Periodic Time. 
Days. 


Ariel 

Umbriel 


119,000 miles. 
166,000 " 
272,000 " 
363,000 " 


2.520383 
4.144121 

8.705897 


Oberon ... 


13.463269 



USEFUL ASTRONOMICAL FACTS. 



393 



THE SATELLITE OF NEPTUNE. 



Name. 


Mean Distance from 
Centre of Neptune. 


Periodic Time. 
Days. 


Anonymous 


220,000 miles. 


5.87690 



I^TDEX. 



Active Volcanoes, Number of, 112. 
Adams, of Cambridge, and Lever- 

rier, of Paris, 249. 
Address of Mr. John Smith, 330. 
Africa would be better known if on 

Moon, 105. 
Air as Blanket to keep Earth Warm, 

8. 
Air not Transparent, 125. 
" Pump, 183. 
" Resistance of, 182. 
Alcor, 343. 
Aldebaran, 389. 
Algol, 342, 385. 
Alpha Centauri, 319; Railway to, 

338. 
Ancient Theory to account for 

Rising and Setting of Sun, 48. 
Andromeda, 385. 

Andromeda, Nebula in, photo- 
graphed by Mr. Roberts, 364. 
Andromedes, 310. 
Annual Motion of Earth rouud Sun, 

56. 
Annular Eclipses, 88. 
Apparent Smallness of Distant Ob- 
jects, 25. 
Appearance of the Sun, 35. 
Appearance of the Sun during a 

Total Eclipse, 40. 
Arctic Sun, 66. 
Area of Moon's Surface, 82. 
Ariel, 243. 

" Distance and Period of, 392. 
Arthur's Seat, Volcano, 114. 
Asaph Hall, Professor, 195. 
Asteroids or Small Planets, 203. 
Astronomer and Mathematician, 

144. 
Astronomers, How they measure 

the Distances of the Heavenly 

Bodies, 19. 
Astronomical Facts, Table of, 391. 
Astronomie, V , A French Journal, 

30. 



Athlete on Moon, 131. 

Atlantic, Sun dropped into, 48. 

Atmosphere of Moon, 125. 

Attraction of Gravitation, 119, 186. 

August Meteors, 309. 

Auriga, 385. 

Auvergne, Ancient Volcanoes in, 

114. 
Awful Vista of Lessons, 371. 
Axis of Earth Constant in Direction, 

69. 



B. 



Babies on the Moon, 130. 

Balloon, How supported, 124. 

Bands on Saturn, 224. 

Bear, Great, 381 ; Little, 383. 

Belts on Jupiter, 215. 

Benefits that we receive from the 
Sun, 10. 

Betelgeuze, 388. 

Biela^s Comet, 311. 

Blanket to keep Earth Warm, 8. 

Books, Number of, Necessary to 
describe L T ni verse, 372. 

Brahe, Tycho, 170. 

Brightness of Saturn, 223. 
" " the Stars, 340. 

" " Sun, 1. 

Brighton Coach, 138. 

British Museum Collection of Mete- 
orites, 313. 

British Natural History Museum, 
370. 

" Brown Bess," 68. 

Brussels, 328. 

Bull, Constellation of the, 388. 

Burning-glass, Experiment with, 3. 

Button illuminated, 152. 

C. 

Cambridge Observations of Nep- 
tune, 251. 
Capella, 385. 
Carigou, Mount, in Pyrenees, 31. 



395 



396 



INDEX. 



Sun 



18. 



Caroline Island, 42. 

Cart-wheel, Measurements with, 

173. 
Cassiopeia, 384. 
Castor and Pollux, 345. 
Celestial Library, 372. 

Size of, 373. 
Changes of the Seasons, 66. 
Changes of the Sun with the Sea- 
sons, 57. 
Charles I., 19. 
Christmas Time, What the 

does for us at, 10. 
Clerk-Maxwell's Top, 182. 
Clock to count Sun's Distance, 
Clouds a Form of Steam, 15. 

" fill our Rivers, etc., 15. 

" on Jupiter, 216. 
" Mars, 191. 
" Neptune, 253. 

" " Saturn, 224. 
" Uranus, 243. 
Cluster in the Centaur, 328. 
Clusters of Stars, 327. 
Coal, Mode of Production of, 11. 

" Whence came it? 11. 
Coal-pit, 201. 
Cock and the Sun, 66. 
Codde, Marcus, Picture of Sunset, 

30. 
Coldness of Mountain Tops, 8. 
Collier, Eye of a, 201. 
Color of Stars, 340. 
Columbiad Theory of Meteorites, 

314. 
Comet attracted by Sun, 274. 

" colliding with Earth, 281. 

" Encke's, 143, 259. 
Comet, Great, of September, 1882, 

277. 
Comet, Halley's, 263. 

" Identification of a, 258. 

" Materials of a, 276. 

" Movements of a, 255. 
of Biela, 311. 

" of 1861, 281. 

" seen at Sun's Edge, 278. 

" Speed of a, 256. 

" Weighing Scales for a, 276. 
Comets and Shooting Stars, 255. 

" Disposition of Tails of, 257. 

" Extravagance of, 283. 

" Tails of, 281. 
Common, Mr., 278. 
Comparative Sizes of Planets, 139. 
Comparison of Solar System and 

Nebula, 367. 



Cooling of Earth and Moon, Illus- 
tration of, 116. 

Copenhagen, Residence of Tycho, 
170. 

Corona of the Sun, 44. 

Cotton Yarn, 334. 

Crape Ring of Saturn, 225. 

Craters on the Moon, 108. 

Craters, Terrestrial and Lunar, 
compared, 113. 

Cricket on the Moon, 131. 

Cunarder's Lights at Sea, 326. 

D. 

Danish Hounds of Tycho Brahe, 172. 
Day and Night, 46, 51. 
Daylight, Stars seen in, 59. 
Deimos and Phobos, Satellites of 

Mars, 200. 
Deimos, Distance and Period of, 391 . 
Desertion, Herschel's, 231. 
Dewar, Professor, 53, 55, 187. 
Dictionary, Worcester's, Use of, 269. 
Dione, Distance and Period of, 392. 
Direction of Earth's Axis Constant, 

69. 
Discoveries of Kepler, 174. 

" " Newton, 178. 

Disguised Stars, 205. 
Disposition of Comets' Tails, 257. 
Distance of the Sun, 17, 210, 391. 
Distances of Heavenly Bodies, How 

measured, 19. 
Distances of Nebulae, 365. 

" the Stars, 332. 
Distant Objects, Apparent Small- 

ness of, 25. 
Double Stars, 342; Motion of, 344. 
D. Q., 210. 

Drawing of the Solar System, 135. 
Dufferin, Lord, 65. 
Dunsink Observatory, Telescope of, 

95. 
Dust from Meteors, 292. 



Eagle in West of Ireland, 27. 
Earth, Annual Motion of, 56. 

" colliding with Comet, 281. 

" Diameter of, 391. 

" Distance of, from Sun, 391. 
Earth, History of, as seen from 

Stars, 337. 
Earth, Internal Heat of, 115. 

" Moon-view of, 78. 



INDEX. 



397 



Earth, Period of, 391. 

" Rank of, in Space, 329. 
" Rotation of, 49, 391. 
" viewed from Sun, 28. 
" Visibility of, 369. 
Eclipse, Total, Appearances seen 

during, 40. 
Eclipses, How produced, 84. 
" Annular, 88. 
" of Jupiter's Satellites, 219. 
" Moon, 89. 
Edinburgh Castle, 114. 
Effect of Moon's Distance on its 

Appearance, 89. 
Electric Lamp, Heating Effect of, G. 
Ellipse, 167 ; Importance of, 169. 

and Parabola, 169, 275. 
Elliptic Paths of Planets, 169. 
Enceladus, Distance and Period of, 

392. 
Encke's Comet, 143, 259; Perio- 
dicity of, 260. 
Eros, 210. 

Eternal Snow on Mountain Sum- 
mits, 9. 
Euclid, 22. 
Evening Star, 151. 
Examining Moon, Quarter the Best 

Time for, 107. 
Experiment with Burning-glass, 3. 
Explosion of Krakatoa, 113. 
Express Train to the Sun, 19. 
Extinct Craters on the Earth, 114 ; 

on the Moon, 114. 
Eye of a Collier, 201. 
Eyes, Use of Two, 19. 

F. 

Facts, Table of Useful Astronom- 
ical, 391. 

Five o'Clock Tea, Sun's Share in, 10. 

Finlay, Mr., 278. 

Flagstaff, Height of, 110. 

Flora, Lawn-tennis on, 209. 

Fly-boats on Royal Canal, Smooth 
Motion of, 52. 

Flying Machines, 208. 

Focus, 5 ; of Ellipse, 170. 

Football on Moon, 131. 

Fossil Trees, 11. 

France, Extinct Craters in, 114. 

Friday, 135. 

G. 

Galle of Berlin finds Neptune, 251. 
Geissler's Tubes, 361. 



Geography of Mars, 188. 

" the Moon, 105. 
George III. and Herschel, 238. 
Georgium Sidus, 240. 
Giant Planets, 212 ; Orbits of, 213. 
Globe, Shadow of, 170. 
Grand Meteors, 295. 
Gravitation, 120, 186. 

on Moon, 128. 

" Small Planets, 209. 

" the Sun, 132. 
Great Bear, 161 ; Number of Stars 

in, 323 ; How to find, 381. 
Green, Mr., 193. 
Greenwich, 138. 
Grinding Specula, 235. 
"Guards," 383. 



Habitability of Moon, 123. 

" Other Worlds, 133. 
Hall, Professor Asaph, 195. 
Halley's Comet, 263 ; Reappearance 

of, 266. 
Heat, Internal, of Earth, 115. 

" of the Sun, 1. 
Heating Effect of Electric Lamp, 6. 
Height of Flagstaff, 110. 

" India-rubber Ball, 19. 
" Meteor, 296. 
" " the Sun, 57. 
Herschel, Caroline, 233, 239. 
William, 230. 

at Windsor, 238. 
Herschel's Saturn, 239. 
"Hoedi," or Kids, 385. 
Holmes, Oliver Wendell, 370. 
Hot Water and the Sun, 14. 
Houzeau, 322. 

How Astronomers measure the Dis- 
tances of the Heavenly Bodies, 19. 
How Planets are weighed, 142. 

" to find the Planets, 390. 

" " name the Stars, 381. 

" " split up a Ray of Light, 351. 
Humming-top, 182. 
Hundreds of Thousands of Libraries 

required, 376. 
Hyperion, Distance and Period of, 

392. 



Iapetus, Distance and Period of, 

392. 
Identification of Comets, 258. 
India-rubber Ball, Height of, 19. 



398 



INDEX. 



Inner Planets, The, 134. 
Insects, Leaf-like, 204. 
Institution, Royal, 53. 
Internal Heat of Earth, 115. 
Inventory of Worlds, 379. 
Iris of the Eye, 202. 
Iron Vapor, 291. 
Island, Caroline, 42. 

j- 

Janssen's Picture of Sun-spot, 3(3. 
Jupiter, 214. 

" compared with Earth, 214. 
Jupiter's Belts, 215. 
Clouds, 216. 
" Diameter, 391. 
" Distance, 391. 
" Internal Heat, 218. 
Jupiter's Period of Revolution, 212, 

391. 
Jupiter's Rotation, 215, 391. 
Satellites, 218. 
" " Eclipses of , 220. 

Jupiter's Satellites, Distances and 

Periods of, 392. 
Jupiter's Weight, 214. 

K. 

Kaiser Sea, 192. 

Kepler, 174 ; His Laws, 177, 186. 
Kilauea, Volcano, 112. 
Kirkwood's Description of Meteor 

Shower, 1833, 301. 
Krakatoa Eruption, 113. 

L. 

Lalande's Observations of Neptune, 

253. 
Latitude defined, 68. 
Lawn-tennis on Flora, 209. 
Law of Motion, First, 183. 
Laws of Kepler, 177. 
Leaf-like Insects, 204. 
Leonids, 308. 

" Orbit of, 302. 
" Letters from High Latitudes, " 65. 
Leverrier, of Paris, and Adams, of 

Cambridge, 249. 
Life on the Moon, 123. 

" " Other Worlds, 369. 

" " Small Planets, 209. 
Light, Velocity of, 219. 
Limit of Visibility, 102. 
Lion, Eyes of, 202. 
Little Bear, 383. 



Little Sunbeam, 17. 
London, Model of, 91. 
Lowell, Mr., 194. 
Lunar Athlete, 131. 

" Babies, 130. 

" Craters, 108. 

Origin of, 111. 

" Cricket and Football, 131. 

" Eclipses, 89. 

" Foxhounds, 131. 

" Geography, 105. 

" Postman, 130. 

" Seas, 108. 

M. 

Magnesium, 350. 

Magnet attracting Ball, 187. 

Man on the Moon, 77. 

Maps of the Stars, 206, 318 ; How to 

make, 389. 
Mars, 134, 160. 

" and his Movements, 160. 

" Atmosphere of, 194. 

" Color of, 161. 
Mars, Diameter and Distance of, 

391. 
Mars, General Direction of Motion 

of, 165. 
Mars, Geography of, 188. 

" Period of, 391. 

" Polar Snows on, 193. 

" Retrograde Motion of, 162. 

" Rotation of, 192, 391. 

" Satellites of, 194. 

" Seas on, 193. 

" Views of, 189, 190. 

" When to observe, 160. 
Materials of a Comet, 276. 
Mathematician and Astronomer, 

144. 
Measurements with a Cart-wheel, 

173. 
Measuring-rod used by Astron- 
omers, 333. 
Mercury, 134, 141. 
Mercury, Diameter, Distance, 

Period, and Rotation of, 391. 
Mercury, Transit of, 142. 
Weight of, 142. 
Where to find, 142. 
Meteor, Height of a, 296. 

of Dec. 21, 1876, 297. 
" Nov. 6, 1869, 292. 
Meteoric Dust, 292. 
Meteorites, 312. 
Meteorites, Columbiad Theory of, 

314. 



INDEX. 



399 



Meteorites in British Museum, 313. 

Meteoroids, 285. 

Meteoroids heated by Friction of 

Air, 288. 
Meteoroids, Velocity of, 286. 
Meteors, 284. 

August, 309. 
Methuselah, 376. 
Milky Way, 327. 

Mimas, Distance and Period of, 392. 
Minor Planets, Size and Number of, 

207. 
Mirror for Reflecting Telescope, 

234. 
Mode of Production of Coal, 11. 
Model of Lunar Crater, 110. 
Monday, Why so called, 74, 135. 
Mont Blanc, 8. 
Moon always shows Same Face, 

118. 
Moon, Imaginary Voyage to, 124. 
Life on, 123. 
" rising in West, 198. 
Size of, 79, 101. 
Moon's Appearance, Effect of Dis- 
tance on, 89. 
Moon's Area, 82. 

" Atmosphere, 125. 
" Diameter, 391. 
" Distance, 391. 
" Movements, 84, 118. 
" Phases 74. 

Time of Revolution, 391. 
Moon-view of Earth, 78. 
Morning Star, 151. 
Motes in Sunbeam, 292. 
Motion, Annual, of Earth, 56. 
Motion of Planet round Sun illus- 
trated, 188. 
Mount Carigou in the Pyrenees, 31. 
Mountains on the Moon, How 

measured, 108. 
Mountain Tops, Coldness of, 8. 

N. 

Naming the Stars, 381. 
Nasmyth, 35. 
National Debt, 339. 
Nature of Saturn's Rings, 225. 
Nebula in Orion, 388. 

" Ring, in Lyra, 354. 
Nebulas, 353. 

Nebulas and Solar System com- 
pared, 367. 
Nebulas, Distances of, 366. 
" Photographs of, 362. 



Nebulas, Stars in, 366. 

What made of, 359. 

Neptune, Discovery of, 244. 

Neptune, Former Observations of, 
252. 

Neptune's Brightness, 252. 
Clouds, 253. 

Neptune's Diameter, Distance, 
Period, and Rotation, 391. 

Neptune's Size, 253. 

Satellite, 253. 

Neptune's Satellite, Distance and 
Period of, 393. 

Neptune's Time of Revolution, 213. 

Newton's Discoveries, 178. 

Night and Day, 46, 51. 

Noonday Gun, 5. 

North Pole, 53; Continual Day at, 
70; Sunshine at, 71. 

November Showers of Meteors, 299. 

Number of Books Necessary to de- 
scribe Universe, 372. 

Number of Minor Planets, 207. 
" Stars, 321. 



Oberon, 243; Distance and Period 

of, 392. 
Objects, Distant, Apparent Small- 

ness of, 25. 
Observing Robes, 172. 
Occupation of Star by Moon, 126. 
Octagon Chapel, Bath, Organist of, 

231. 
Old Moon in New Moon's Arms, 77. 
Orbit of Leonids, 302. 
Orbits of Giant Planets, 213. 

" " Uranus and Neptune, 250. 
Orion, 387. 
Oxygen Necessary to Life, 124. 



Pacific Ocean, Track of Eclipse 

across, 42. 
Parabola, 169, 269. 

and Ellipse, 169, 275. 
Parabolic Reflectors, 272. 
Pegasus, Square of, 384. 
Pendulum, 54. 
Periodicity of Comets, 263. 
Perseids, 309. 
Perseus, 327, 385. 

Perturbation of Encke's Comet, 146. 
Phases of Mercury, 142. 
" " the Moon, 74. 



400 



INDEX. 



Phases of Venus, 152. 

Phobos and Deimos, Satellites of 

Mars, 200. 
Phobos, Distance and Period of, 391. 
Phoebe, 229. 
Photographic Search for Planets, 

207. 
Photographing the Nebulae, 362. 
Photographs of the Heavenly 

Bodies, 207. 
Photographs of the Moon, 107, 109. 
Pit-eyes, 201. 

Planetary Time Table, 179. 
Planets, How to find the, 390. 
" Small, or Asteroids, 203. 
" Small, Search for, 205. 
Planets, Small, Size and Number of, 

207. 
Pleiades, 363, 385 ; Apparent Change 

in Position of, 387. 
"Pointers," 383. 
Polar Snows on Mars, 193. 
Pole, North, 53; Continual Day at, 

70; Sunshine at, 71. 
Pole Star, 383. 
Postman on the Moon, 130. 
Prediction of Halley, 264. 
Preserved Sunbeams, 13. 
Prism, Refraction of Light through, 

351. 
Prominences on Sun, 44. 
Proportion of Sunlight received by 

Earth, 9. 
Pupil of the Eye, 201. 
Pupil of the Eye as Large as a 

Dinner Plate, 203. 

Q. 

Quarter the Best Time for examin- 
ing the Moon, 107. 
Quicksilver, 141. 



Radiant Point of Meteor Shower, 
308. 

Railway to Alpha Centauri, 338. 

Rank of Earth in Space, 329. 

Reappearance of Halley's Comet, 
267. 

Recorder, Sunshine, 5. 

Reflectors for Lighthouses, 271. 

Refraction of Light through Prism, 
351. 

Relative Sizes of Earth and Sun, 31. 

Requisites for Astronomical Dis- 
coveries, 199. 



Resistance of Air, 182. 

Retrograde Motion of Mars, 162. 

Rhea, Distance and Period of, 392. 

Rifle, 68. 

Rigel, 388. 

Ring Nebula in Lyra, 354. 

Rings of Saturn, 224. 

Rings of Smoke, 357. 

Rising and Setting of Sun, Ancient 
Theories of, 48. 

Roberts, Mr. Isaac, 325; His Photo- 
graph of Great Andromeda Neb- 
ula, 364. 

Rotating Globe of Oil, 215. 

Rotation of Earth, 49. 

Rotation of Earth, Illustration of, 
53. 

Rotation of Jupiter, 215. 
" Mars, 192. 
" " Sun, 39. 

Rowton Meteorite, 313. 

Royal Canal Fly-boats, 52. 

Royal Institution, 53. 



St. Paul's Cathedral on the Moon, 

103. 
Sandwich Isles, Crater in the, 112. 
Satellites, 195. 

" of Jupiter, 218. 

" Mars, 194. 
" Saturn, 229. 
Satellites of Uranus, Revolution of, 

243. 
Saturday, 135. 
Saturn, 222. 

" and Earth, 223. 
Saturn's Bands and Clouds, 224. 

" Brightness, 223. 
Saturn's Diameter and Distance, 

391. 
Saturn's Internal Heat, 224. 
Period, 391. 
Rings, 224. 
Rotation, 391. 
Satellites, 229. 
Saturn's Satellites, Distances and 

Periods of, 392. 
Saturn's Time of Revolution, 212. 
Scale of Universe, 319. 
Search for Small Planets, 205. 
Seas on Mars, 193. 

" " the Moon, 108. 
Seasons, Changes of the, C)(j. 
Seasons, Changes of the Sun with 
the, 57. 



INDEX. 



401 



Seen and Unseen Universe, 377. 
Shadow of Globe, 170. 
Shape and Size of the Sun, 29. 
Shooting Stars and Comets, 255. 
Shooting Stars, What becomes of 

them, 290. 
Sidus, Georgium, 240. 
Sirius, 318. 

" How to find, 389. 
Sirius, Position of, on Map of Uni- 
verse, 319. 
Size of Celestial Library, 373. 
" Minor Planets, 207. 
" Moon, 79, 101. 
" the Sun, 29. 
Sizes, Comparative, of Planets, 139. 
Sizes, Comparative, of Earth and 

Sun, 31. 
Smith, Mr. John, his Address, 330. 
Smoke Rings, 357. 
Snow on Mountain Tops, 9. 
Snowball, 294. 
Sodium, 350. 
Solar Gravitation, 132. 

" Prominences, 44. 
Solar System and Nebula compared, 

367. 
Solar System, Drawing of the, 135. 
Spectroscope, 352. 
Speculum Grinding, 235. 

Metal, 235. 
Speed of Planets, 138. 
Splendor of Venus, 151. 
Spots on the Sun, 33. 
Square of Pegasus, 384. 
Star eclipsed or occulted by Moon, 

126. 
Star Maps, 206, 318 ; How to make, 

389. 
Stars, 318; Number of, 321. 

" are Suns, 320. 

" Clusters of, 327. 

" Disguised, 205. 

" Distances of, 332. 

" Double, 342; Motion of, 344. 

" How to name the, 381. 

" seen in Daylight, 59. 

" Variable, 341. 

" What made of, 347. 
Steam, Clouds a Form of, 15. 
Steel melted by Sunbeams, 7. 
Strontium, 348. 

Sun and Sirius compared in Bright- 
ness, 320. 
Sun, Benefits that we receive from 

the, 10. 
Sun, Express Train to, 18. 



Sun must be Hotter than Molten 

Steel, 7. 
Sun's Appearance, 35. 

" Attraction on a Comet, 274. 

" Corona, 44. 

" Diameter, 391. 

" Distance, 17, 158, 210, 391. 

" Heat and Brightness, 1. 

" Rotation, 39, 391. 

" Shape and Size, 29. 

' ' Share in Five o'Clock Tea, 10. 

" Spots, 33. 

" Sunbeams, Preserved, 13. 
Sunday, 74, 135. 
Sunlight, Proportion of, received by 

Earth, 9. 
Sunset at Marseilles, 30. 
Sunshine at North Pole, 71. 
" Recorder, 5. 

T. 

Tails of Comets, 281. 
Telegraph used for Comets, 267. 
Telescope of Dunsink Observatory, 

96. 
Telescope of Yerkes Observatory, 

98. 
Telescopes, 92; Reflecting, 232; 

Herschel's, 233. 
Telescopic Aid, 200. 

" View of Moon, 101, 104. 

Tethys, Distance and Period of, 392. 
Theory to account for the Sun's 

Rising and Setting, 48. 
Thursday, 135. 

Ticket to Alpha Centauri, 339. 
Time occupied by Light and Stars, 

335. 
Titan, Distance and Period of, 392. 
Titania, 243. 
Titania, Distance and Period of, 

392. 
Top-spinning under Air Pump, 183. 
Total Eclipse of the Sun, Appear- 
ances during, 40. 
Toy, Burning-glass not merely a, 6. 
Train to the Sun, 18. 
Transit of Venus, 154. 
Trouvelot's Drawing of Eclipse, 41. 
Trouvelot's Drawing of Solar 

Prominences, 45. 
Tuesday, 135. 
Twilight, 47. 

Two Eyes Better than One, 19. 
Tycho Brahe, 170. 
Tycho's Method of Observing, 172. 



402 



INDEX. 



Tyndall's, Professor, Heating Effect 
of Electric Lamp, 6. 

U. 

Umbriel, 243. 

Umbriel, Distance and Period of, 

392. 
Universe, Seen and Unseen, 377. 
"Up, Guards, and at them," 337. 
Uranus and Earth compared, 243. 
Uranus, Clouds on, 243. 
" Color of, 242. 
" Diameter of, 391. 
" Discovery of, 237. 
" Distance of, 391. 
Uranus, Former Observations of, 

241. 
Uranus, Period of, 391. 

Rotation of, 391. 

Satellites of, 242. 

Uranus, Satellites of, Distances and 

Periods of, 392. 
Uranus, Time of Revolution, 213. 

Weight of, 243. 
Ursa Major, or Great Bear, 381. 
Use of Two Eyes, 19. 
Utility of Telescope, 200. 



Vapor of Iron, 291. 
Variable Stars, 341. 
Vega, 337. 
Velocity of a Planet, 138. 

" " Light, 219. 
Venus, 134, 150. 

Venus, Appearance of, during Tran- 
sit, 157. 
Venus as a World, 158. 

" Composition of Air on, 160. 
Venus, Diameter and Distance of, 

391. 
Venus, Gravitation on, 159. 

" Greatest Brilliance of, 152. 



Venus, in Telescope, 151. 

" Period and Rotation of, 391. 
Venus, Sun's Distance deduced from 

Transit of, 158. 
Venus, Temperature of, 159. 

Transit of, 154. 
Venus, When and where to seek, 

150. 
View of Earth from the Sun, 28. 
Views of Lunar Scenery, 104, 109. 

" " Mars, 189, 190. 
Visibility, Limit of, 102. 
of Earth, 369. 
Volcanoes, Number of, 112. 
Voyage to the Moon, 124. 

" Sun, 2. 
Vulcan, 48, 49, 57. 

W. 

Waste of the Tail-making Material 

of Comets, 283. 
Water, Hot, and the Sun, 14. 
Water-mill turned by Sun, 16. 
Water on Moon, 127. 
Waterloo, 68, 337. 
Wednesday, 135. 
Weighed, How Planets are, 142. 
Weighing Scales for Comets, 276. 
Weight of Jupiter, 214. 
" " Mercury, 149. 
" " Uranus, 243. 
Weights on the Moon, 127. 

" " Sun, 132. 
What Nebulae are made of, 359. 

" Stars are made of, 347. . 
Wind, Cause of, 14. 
Wind-mill turned by Sun, 15. 
Worcester's Dictionary, Use of, 269. 

Y. 

Yellowstone Park, 115. 
Yerkes Observatory, Chicago, Tele- 
scope at, 98. 



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